SCHEDULE 14A INFORMATION
                    PROXY STATEMENT PURSUANT TO SECTION 14(a)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

Filed by the registrant [X]
Filed by a party other than the registrant [_]

Check the appropriate box:
[_]   Preliminary Proxy Statement
[_]   Confidential, for Use of the Commission Only (as permitted by
      Rule 14a-6(e)(2))
[_]   Definitive Proxy Statement
[_]   Definitive Additional Materials
[X]   Soliciting Material Under Rule 14a-12

                              MKS INSTRUMENTS, INC.
                (Name of Registrant as Specified in Its Charter)

    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of filing fee (Check the appropriate box):

[X]   No fee required
[_]   $125 per Exchange Act Rules 0-11(c)(1)(ii), 14a-6(i) (1), 14a-6(i)(2) or
      Item 22(a) of Schedule 14A.
[_]   Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

      (1)  Title of each class of securities to which transaction applies:
      (2)  Aggregate number of securities to which transaction applies:
      (3)  Per unit price or other underlying value of transaction computed
           pursuant to Exchange Act Rule 0-11 (Set forth the amount on which the
           filing fee is calculated and state how it was determined):
      (4)  Proposed maximum aggregate value of transaction:
      (5)  Total fee paid:

[_]   Fee paid previously with preliminary materials.

[_]   Check box if any part of the fee is offset as provided by Exchange Act
      Rule 0-11(a)(2) and identify the filing for which the offsetting fee was
      paid previously. Identify the previous filing by registration statement
      number, or the form or schedule and the date of its filing.

      (1)  Amount previously paid:
      (2)  Form, schedule or registration statement no.:
      (3)  Filing party:
      (4)  Date filed:

                                                  Filed by MKS Instruments, Inc.
               Pursuant to Rule 14a-12 under the Securities Exchange Act of 1934
                                          Subject Company: MKS Instruments, Inc.
                                                    Commission File No.: 0-23621

SAFE HARBOR PASSAGE

Statements in this filing regarding the benefits of the proposed business
combination transaction, including future financial and operating results,
timing of the closing of the transaction, and the benefits of the transaction,
are forward-looking statements within the meaning of the "safe harbor"
provisions of the Private Securities Litigation Reform Act of 1995. These
statements are based on management's current expectations or beliefs and are
subject to a number of factors and uncertainties that could cause actual results
to differ materially from those described in the forward-looking statements. The
following important factors, among others, could cause actual results to differ
materially from those described in the forward-looking statements: failure of
MKS' stockholders to approve the transaction; costs related to the transaction;
the difficulty the market may have in valuing the MKS/ENI business model; the
risk that MKS' and ENI's businesses will not be integrated successfully; the
failure of the combined business to realize anticipated benefits of the
transaction; and other economic, business, competitive and/or regulatory factors
affecting MKS' business generally, including those factors set forth in the
company's filings with the Commission, including the most recent Annual Report
on Form 10-K and Quarterly Report on Form 10-Q. MKS is under no obligation to,
and expressly disclaims any obligation to, update or alter its forward-looking
statements, whether as a result of new information, future events or otherwise.

THE FOLLOWING PRESS RELEASE WAS ISSUED ON WEDNESDAY, OCTOBER 31, 2001:

[MKS LOGO]

                                                           FOR IMMEDIATE RELEASE

                                                     INVESTOR RELATIONS CONTACT:
                                                                  Ronald Weigner
                                        Vice President & Chief Financial Officer
                                                           MKS Instruments, Inc.
                                                                    978.975.2350
                                                         ron_weigner@mksinst.com

            MKS INSTRUMENTS ANNOUNCES DEFINITIVE AGREEMENT TO ACQUIRE
                          THE ENI DIVISION OF EMERSON


     COMBINATION CREATES BROAD SUBSYSTEM SUPPLIER TO THE SEMICONDUCTOR AND
                          THIN FILM EQUIPMENT INDUSTRY.

                   ADDS COMPLEMENTARY RF AND DC POWER DELIVERY
                  SUBSYSTEM PRODUCTS TO MKS' PRODUCT PORTFOLIO

         October 31, 2001, Andover, Mass. -- MKS Instruments, Inc. (NASDAQ:
MKSI), a leading supplier of gas measurement, control and analysis products used
in semiconductor and other advanced thin-film manufacturing processes, today
announced that it has entered into a definitive agreement to acquire the ENI
division of Emerson (NYSE: EMR). ENI is a leading supplier of solid-state radio
frequency (RF) and direct current (DC) plasma power supplies, matching networks
and instrumentation to the semiconductor and thin-film processing industries.
The acquisition further expands MKS' comprehensive suite of products and is part
of the Company's ongoing strategy to augment its product and technology
portfolio, and to provide higher added value subsystems for its key OEM and
end-user customers. ENI, based in Rochester, NY, is a global company that
employs more than 600 people worldwide. ENI has R&D, engineering and
manufacturing operations in the United States and Asia and a worldwide sales and
service organization.

         Under the terms of the agreement, MKS will issue 12 million shares of
common stock to Emerson in exchange for the businesses and assets of ENI. Based
on MKS' closing stock price on October 30, 2001 of $20.91, the transaction is
valued at $251 million. MKS will also assume approximately $3.5 million of net
debt. The Board of Directors of MKS has unanimously approved the transaction.
Completion of the acquisition is subject to customary closing conditions,
including the approval of MKS' shareholders. After the close of the transaction,
Emerson will own approximately 24 percent of MKS' outstanding stock, and Emerson
President James Berges will join the MKS Board of Directors. The transaction is
expected to be completed in the first calendar quarter of 2002 and is
anticipated to be accretive to MKS' cash earnings per share in 2002 without the
inclusion of synergies.

         ENI's products will become part of a technologically advanced product
family that includes MKS' pressure management subsystems, vacuum subsystem
products, advanced materials delivery products, process monitor products,
digital process control network products, plasma and reactive gas generator
products, and FTIR - based gas and thin-film measurement products.

         ENI's products complement the portfolio of MKS' ASTeX Products group,
the leading supplier of plasma and reactive gas solutions. The acquisition adds
critical solid-state power conversion technology to MKS' core capability in
plasma management, and enables MKS to offer more highly integrated and higher
performance products to its OEM and end-user customers. ENI will become the ENI
Products group of MKS. The operations of ENI Products will continue to be
managed by ENI's current President, Ed Maier, who will become Vice President and
General Manager, ENI Products, and will report to Dr. Peter Younger, President
and Chief Operating Officer of MKS.

         The transaction is consistent with MKS' objective of expanding its core
technologies and product offering through strategic acquisitions. MKS Chairman
and CEO John Bertucci said, "By combining ENI's strength in power delivery
subsystems and ASTeX's expertise in reactive gas generation and plasma
technology, we are confirming MKS' commitment to providing our customers with
application solutions for their leading edge products. Together, we will
increase our critical mass, broaden our technology base and strengthen our
ability to serve our customers."

         James Berges stated further, "We, at Emerson, are excited about this
strategic combination and look forward to remaining a long-term partner and
supporter of MKS. ENI is a power conversion company, but its focus on the
semiconductor capital equipment market is not mainstream to Emerson's Network
Power business. Nevertheless, we like the long term, through-the-cycle growth
characteristics of semiconductors, and see the combination of MKS and ENI as a
way to realize broader and deeper participation in this market."

         Management will host a conference call on Wednesday, October 31 at 8:00
a.m. (EST) to discuss the transaction. To participate on the audio portion of
the call, please dial 800-219-6110 (domestic) or 303-262-2130 (international) at
least five minutes before start time.

         For further information on ENI's products and technology, visit
www.enipower.com. For information on MKS and to view a presentation related to
the transaction, visit www.mksinst.com.

--------------------------------------------------------------------------------

MKS Instruments, Inc. is a leading worldwide developer, manufacturer and
supplier of instruments, components and subsystems used to measure, control, and
analyze gases in semiconductor manufacturing and similar industrial
manufacturing processes and a leading developer, manufacturer and supplier of
reactive gas generation and power delivery products. MKS Instruments, Inc. sold
products to more than 4,000 customers in 2000. In addition to semiconductors,
MKS' products are used in processes to manufacture a diverse range of products,
such as optical filters, fiber optic cables, flat panel displays, magnetic and
optical storage media, medical equipment, architectural glass, solar panels and
gas lasers.

This report may contain projections or other forward-looking statements
regarding future events or the future financial performance of MKS. These
projections or statements are only predictions. Actual events or results may
differ materially from those in the projections or other forward-looking
statements set forth herein. Among the important factors that could cause actual
events to differ materially from those in the projections or other
forward-looking statements are the challenges and risks involved with
integrating the operations of MKS and ENI, potential fluctuations in quarterly
results, dependence on new product development, rapid technological and market
change, acquisition strategy, manufacturing and sourcing risks, volatility of
stock price, international operations, financial risk management, and future
growth subject to risks. Readers are referred to MKS' filings with the
Securities and Exchange Commission, including its most recent filings on Form
10-K and 10-Q, for a discussion of these and other important risk factors
concerning MKS and its operations.

                                       ###

SLIDES:


Slide #1


                              MKS INSTRUMENTS, INC.

                          Strategic Acquisition of ENI
                                 31 October 2001

       [MKS LOGO]
Technology for Productivity

     -           ASTeX(R)
     -           Baratron(R)
     -           D.I.P.(TM)
     -           HPS(R)
     -           Mass-Flo(R)
     -           On-Line(TM)
     -           Spectra(TM)
     -           ENI


                                                                               1

Slide #2                                                              [MKS LOGO]

Introduction

                                  JOHN BERTUCCI
                       Chairman & Chief Executive Officer
                                 MKS Instruments

                                  JAMES BERGES
                                    President
                                     Emerson

                                   RON WEIGNER
                    Vice President & Chief Financial Officer
                                 MKS Instruments



                                                                               2

Slide #3

                                                                     [MKS LOGO]

SAFE HARBOR PASSAGE

This presentation may contain forward-looking statements that are made under the
safe harbor provisions of the Securities Litigation Reform Act of 1995. Such
statements are estimates which involve risks and uncertainties. Actual results
may vary significantly from those stated in forward-looking statements. Further
information regarding risk factors can be found in the Company's filings with
the Securities and Exchange Commission.


                                                                               3

Slide #4

                    TRANSACTION SUMMARY & STRATEGIC OVERVIEW

                                  John Bertucci

                                 Chairman & CEO

                                 MKS Instruments
       [MKS LOGO]
Technology for Productivity

     -           ASTeX(R)
     -           Baratron(R)
     -           D.I.P.(TM)
     -           HPS(R)
     -           Mass-Flo(R)
     -           On-Line(TM)
     -           Spectra(TM)
     -           ENI



                                                                               4

Slide #5                                                             [MKS Logo]

TRANSACTION SUMMARY

  STRUCTURE                -        MKS stock issued to Emerson in exchange for
                                    businesses and assets of ENI

  CONSIDERATION            -        12 million shares of MKS common stock (23%
                                    of pro forma MKS common stock*)

  BOARD MEMBERSHIP         -        James Berges, President of Emerson

  EMERSON'S MKS SHARES     -        One year lock-up; subsequent registration
                                    rights

  KEY CLOSING CONDITIONS   -        MKS stockholder approval
                           -        Other customary approvals

  EXPECTED CLOSING         -        Q1 2002



* Fully diluted shares outstanding based on treasury stock method as of
  October 30, 2001.

                                                                               5

                                                                      [MKS Logo]

Slide #6

COMPLEMENTARY TECHNOLOGIES...
INTEGRATED SOLUTIONS

[MKS logo]
Technology for Productivity

-    Leading OEM subsystem solution provider for gas & vacuum-based processes

-    High-value, integrated product offerings for diverse and growing markets

-    Positioned to benefit from supply chain evolution

-    World-class global infrastructure

-    Successful integrator of strategic acquisitions

[ENI logo]

-    Leading supplier of RF and DC plasma power supplies, matching networks and
     instrumentation to the semiconductor and thin film processing industries

-    Strong OEM customer base

-    Global footprint

-    Strong financial performance

-    Seasoned management team


                                                                               6

                                                                      [MKS LOGO]

Slide #7

STRATEGIC COMBINATION FOR
PROFITABLE GROWTH

-    Adds critical solid-state power conversion technology to MKS' portfolio

-    MKS' plasma and ENI power delivery highly synergistic

-    Offers more highly integrated and higher value/performance products

-    Leverages R&D investment

-    Customer and Market diversity

-    Leverages global infrastructure and supply chain management

-    Strong geographical and cultural fit

-    Augments MKS' position as a leading provider of OEM subsystem solutions to
     the semiconductor capital equipment industry

-    Expected to be accretive to MKS' cash EPS in 2002 (without inclusion of
     synergies)


                                                                               7

                                                                      [MKS LOGO]

Slide #8

SUPPLY CHAIN EVOLUTION



          Chip                                                 Capital                               Instrument
        Design &      Chip         Process       Process      Equipment    Subsystem    Subsystem    Component
       Marketing   Manufacture   Integration   Development   Manufacture    Design     Manufacture   Technology
                                                                             
70's      FAB         FAB            FAB           FAB           FAB          FAB          FAB           MKS
80's      FAB         FAB            FAB           FAB           OEM          OEM          OEM           MKS
90's      FAB         FAB            FAB           OEM           OEM          OEM          MKS           MKS
Now       FAB         FAB            OEM           OEM           OEM          MKS          MKS           MKS


                                                                               8

                                                                      [MKS LOGO]


Slide #9

CRITICAL PROCESS TECHNOLOGIES...
GROWING MARKETS

[First part of diagram shows the following Semiconductor processes:

            RTP
            Epi
            Etch
            CMP
            Diffusion
            Vacuum Processes
            Strip
            Ion Implant
            Clean
            CVD
            PVD
            ECD
            SEM

"~two thirds of wafer fab processes are controlled by MKS' products"

"virtually every chip in the world is made with MKS' products"]

[Second part of the diagram shows applications, other than semiconductor, which
are made using the same processes, specifically

            Flat Panel Displays
            Micro-Machined Devices
            MRI
            Magnetic/Optical Storage Media
            Freeze Dried Pharmaceuticals
            Sterilized Medical Instruments
            Optical Filters & Fibers
            LEDs
            Solar Cells
            Lasers]

[Third part of diagram shows the growing markets that use these products,
specifically

            Telecommunications
            Internet Infrastructure
            Consumer Electronics
            Pharmaceutical & Medical
            PCs
            Automotive Electronics]


                                                                               9

                                                                      [MKS LOGO]

Slide #10

MKS CORE PRODUCTS

[Diagram of the process chamber, including the following products:

            Materials Delivery System
            Gas Panel Instruments
            Gas Box Instruments]

[Diagram of process chamber described above, adding on:

            Process Monitor
            Pressure Measurement]

[Diagram of process chamber described above, adding on:

            Control Valve
            Adaptive Controller
            Vacuum Components/Subsystems]

[Diagram of process chamber described above, adding on:

            Digital Control Network]

[Diagram of process chamber described above, adding on:

            Ozone Generator]

[Diagram of process chamber described above, adding on:

            Reactive Gas Generators]

[Diagram of process chamber described above, adding on:

            Power Generators

            uW]

[Diagram of process chamber described above, adding on:

            Gas Monitor]

[Diagram of process chamber described above, adding on:

            Exhaust Monitor]

[Diagram of process chamber described above, adding on:

            Wafer Monitor]

[Diagram of process chamber described above, adding on each of the ENI products:

            RF Match
            RF
            DC]


                                                                              10

                                                                      [MKS LOGO]

Slide #11

COMPREHENSIVE PRODUCT OFFERINGS

[Photos of product from the following product groups:

          Pressure Measurement & Control
          Materials Delivery
          Spectra
          On-Line
          D.I.P.
          ASTeX
          ENI
          HPS]

Integrated Subsystems

*    Improve Productivity & Performance
*    Reduce Size & Manufacturing Complexity
*    Reduce Customer Total Cost


                                                                              11

                                                                      [MKS LOGO]

Slide #12

DELIVERING INTEGRATED SUBSYSTEMS

[Slide shows pictures of the following integrated subsystems

            Helium Cooling Subsystem
            Flow Verification Subsystem
            Effluent Management Subsystem
            Pressure Control Subsystem
            Resist Strip Subsystem
            Chamber Clean Subsystem]


                                                                              12

                                                                      [MKS Logo]

Slide #13

Industry Landscape



                             Vacuum    Vacuum                     Leak              Digital
         Pressure   Flow   Components  Gauges    Subsystems   Detectors    Monitor  Network


                                                            
MKS         X         X         X         X           X           X           X
Aera                                                  X
Edwards                         X         X                       X
Helix                                     X                                            X
Inficon                         X         X                       X           X
MDC                             X
Mykrolis    X         X
Nor-Cal                         X
STEC                  X
Unit                  X
Varian                          X         X                       X
AE
Analogic
Daihen
Ebara
Sumitomo






                                Reactive
            Ozone    Liquozone    Gas       uW       FTIR
                                           Power

                                      
MKS           X          X         X            X        X
Aera
Edwards
Helix
Inficon
MDC
Mykrolis
Nor-Cal
STEC
Unit
Varian
AE                                 X
Analogic
Daihen                                          X
Ebara         X          X
Sumitomo      X          X







         Solid-State                    RF Matching
         RF Power      DC Power         Networks         V/I Sensors
                                             
ENI          X             X                X                 X
Aera
Edwards
Helix
Inficon
MDC
Mykrolis
Nor-Cal
STEC
Unit
Varian
AE           X             X                X                 X
Analogic     X
Daihen       X                              X
Ebara
Sumitomo


Source: Company estimates of market participants with share >5%


                                                                              13

                                                                      [MKS LOGO]

Slide #14

CUSTOMER & MARKET DIVERSITY
4,000+ ACTIVE CUSTOMERS WORLDWIDE



          SEMICONDUCTOR CAPITAL EQUIPMENT                                  SEMICONDUCTOR MANUFACTURERS
          -------------------------------                   -------------------------------------------------------------------
                                                                                            
[ ] Applied Materials            [ ]  Novellus              [ ]  AMD           [ ] Mitsubishi           [ ] ST Microelectronics
[ ] ASM                          [ ]  Semitool              [ ]  Fujitsu       [ ] Motorola             [ ] Siemens
[ ] Axcelis                      [ ]  Silicon Valley        [ ]  Hitachi       [ ] National Semi        [ ] TI
[ ] Genus                             Group (ASML)          [ ]  Hyundai       [ ] NEC                  [ ] Toshiba
[ ] Hitachi                      [ ]  Tokyo Electron        [ ]  IBM           [ ] Philips              [ ] TSMC
[ ] Lam Research                 [ ]  ULVAC                 [ ]  Intel         [ ] Samsung              [ ] UMC
                                 [ ]  Varian                [ ]  Micron




                                                              SPECIALTY
              DATA STORAGE AND FPD                           GAS SUPPLIERS                   DIVERSE PROCESSES
              --------------------                           -------------                ------------------------
                                                                                          
[ ] AKT                          [ ]  NEC                  [ ]  Air Liquide         [ ] Abbott Labs   [ ] GE
[ ] Alcatel                      [ ]  Seagate              [ ]  Air Products        [ ] Delco         [ ] Johnson & Johnson
[ ] Anelva                       [ ]  Sharp                [ ]  BOC                 [ ] Ford          [ ] Philips Medical
[ ] CVC                          [ ]  Toshiba              [ ]  Kinetics                              [ ] OSRAM
[ ] Komag                        [ ]  Unaxis               [ ]  Nippon Sanso                          [ ] Westinghouse
[ ] Lucent                       [ ]  Veeco                [ ]  Praxair


Source: Internal MKS and ENI information. ENI information adjusted for MKS
fiscal year.


                                                                              14

                                                                      [MKS LOGO]

Slide #15

ESTABLISHED GLOBAL INFRASTRUCTURE

[Diagram of world showing locations of MKS facilities and ENI locations]

-           12 MKS Manufacturing Facilities
-           34 MKS Customer Support Centers
-           New ENI Locations


                                                                              15

Slide #16

                              ENI COMPANY OVERVIEW

[MKS Logo]                         James Berges

Technology for Productivity         President

                                Emerson Electric


          -           ASTeX(R)
          -           Baratron(R)
          -           D.I.P.(TM)
          -           HPS(R)
          -           Mass-Flo(R)
          -           On-Line(TM)
          -           Spectra(TM)
          -           ENI



                                                                              16

Slide #17                                                             [MKS Logo]

EMERSON VIEWPOINT

-            Long-term partnership

-            Powerful strategic combination

-            Broader participation in semiconductor OEM market


                                                                              17

Slide #18                                                             [MKS Logo]

ENI OVERVIEW

-        ENI founded in May 1969 and was acquired by Emerson in 1999 as part of
         acquisition of Astec (BSR) plc

-        ENI's product suite includes

[Slide shows pictures of the following products:

            DC Generators
            RF Generators
            RF V/I Probes
            RF Match]


                                                                              18

Slide #19                                                             [MKS Logo]

ENI PROCESS APPLICATIONS

[Slide shows the semiconductor processes and applications, other than
semiconductor, specifically

            RTP
            Epi
            Etch
            CMP
            Diffusion
            Vacuum Processes
            Strip
            Ion Implant
            Clean
            CVD
            PVD
            ECD
            SEM
            Flat Panel Displays
            Micro-Machined Devices
            MRI
            Magnetic/Optical Storage Media
            Freeze Dried Pharmaceuticals
            Sterilized Medical Instruments
            Optical Filters & Fibers
            LEDs
            Solar Cells
            Lasers

highlighting the applications of ENI products, specifically

            Etch
            Strip
            Ion Implant
            CVD
            PVD
            ECD]


                                                                              19


Slide #20

                               FINANCIAL OVERVIEW

                                   Ron Weigner
[MKS Logo]
                              Vice President & CFO
Technology for Productivity
                                 MKS Instruments


     -           ASTeX(R)
     -           Baratron(R)
     -           D.I.P.(TM)
     -           HPS
     -           Mass-Flo(R)
     -           On-Line(TM)
     -           Spectra(TM)
     -           ENI



                                                                              20

Slide #21
                                                                      [MKS Logo]
PRO FORMA FINANCIAL STATISTICS
LTM IN # MILLIONS (1)



                                                       MKS                   ENI                 COMBINED                 ENI %
                                                       ---                   ---                 --------                 -----
                                                                                                              
         REVENUE                                      $380.6               $108.9                  $489.5                   22.2%

         GROSS PROFIT                                  147.2                 47.0                   194.2                   24.2%

         EBITA(2)                                       29.9                 20.7                    50.6                   40.9%

         CASH NET INCOME                                22.9                 12.3                    35.2                   34.9%


EXPECTED TO BE ACCRETIVE TO MKS' 2002 CASH EPS (WITHOUT INCLUSION OF SYNERGIES)

(1) Financial information excludes non-recurring charges; ENI historical
information pro forma to eliminate Emerson internal charges and to add estimated
changes of being a stand-alone entity

(2) Excluding non-recurring charges and Other Income and Expense.

                                                                              21

                                                                      [MKS Logo]

Slide #22

TOP 10 CUSTOMERS (LTM)



  MKS                                      ENI                                   COMBINED
  ---                                      ---                                   --------
                                                                         
- Air Products                           - Applied Materials                   - Applied Materials
- Applied Materials                      - Lam                                 - Intel
- Intel                                  - March Instruments                   - Kinetics
- Kinetics                               - Novellus                            - Lam
- Lam                                    - Philips Medical                     - Novellus
- Novellus                               - STS                                 - Philips Medical
- Philips Medical                        - TEL                                 - TEL
- TEL                                    - Ulvac                               - Ulvac
- Ulvac                                  - Unaxis                              - Unaxis
- Varian                                 - Veeco                               - Varian



                                                                              22

                                                                      [MKS Logo]

Slide #23

PRO-FORMA REVENUE MIX

[Pie chart showing Revenue by Industry as follows:

          Semiconductor Equipment -- 75%
          Semi Fabs -- 6%
          Pharm., Diverse, Vacuum -- 11%
          Other Thin Film -- 7%]

[Pie chart showing Revenue by Region as follows:

          US -- 74%
          Asia -- 16%
          Europe -- 10%]

* Calendar Year 2000 Combined


                                                                              23

                                                                      [MKS Logo]

Slide #24

PRO FORMA HISTORICAL PERFORMANCE *

[Graphical display showing MKS' Revenue from 1997 through 2000 and LTM ranging
from approximately $140M to $494M; MKS' EBITA from 1997 through 2000 and LTM
ranging from approximately $9M to $96M; and ENI's Revenue for 2000 and LTM
ranging from approximately $109M to $123M; ENI's EBITA for 2000 and LTM ranging
from approximately $20M to $32M]

Pro Forma EBITA Margin
     1997-13%
     1998- 6%
     1999-15%
     2000-21%
      LTM-10%

* Pro Forma for ASTeX combination for 2000 and LTM only. Excluding non-recurring
charges and Other Income and Expense.


                                                                              24

                                                                      [MKS Logo]

Slide #25

PRO-FORMA COMBINED BALANCE SHEET



                  ($ MILLIONS)                              SEPT 30, 2001
                  ------------                              -------------
                                                         
                  Cash Investments                                $148.7

                  Total Debt                                       $38.8

                  Stockholders' Equity*                           $614.9

                  Current Ratio                                      4.8


*Based on valuing transaction shares at the MKS closing price on October 30,
2001.


                                                                              25

                                                                      [MKS Logo]

Slide #26

EMERSON'S MKS SHARES

[Pie chart showing Pro Forma Ownership as follows:

     Management -- 3.6%
     Principal Shareholders -- 29.6%
     Emerson -- 23.3%
     Retail -- 12.3%
     Top 15 Institutions -- 20.6%
     Other Institutions -- 10.6%]

EMERSON REGISTRATION RIGHTS AND RESALE RESTRICTIONS

Transfer Restrictions         5% Maximum

Lock-Up                       1 Year

Registration Rights
--   Number                   3

--   Terms                    Maximum of 1 per 12 month period, share number
                              cumulatively and evenly spread on monthly basis
                              after lock-up period expires

Minimum Size                  2 million shares

* Fully diluted shares outstanding based on treasury stock method as of
  October 30, 2001.
                                                                              26


                                                                      [MKS Logo]

Slide #27

SUMMARY

-    Strengthens leadership as OEM subsystem solutions provider

-    Complementary MKS plasma and ENI power supply products provide higher
     value, world-class plasma delivery subsystems

-    Leverage infrastructure, supply chain management and R&D

-    Strong foundation for higher growth and profitability

-    Expected to be accretive to MKS' cash EPS in 2002 (without inclusion of
     synergies)
                                                                              27

Slide #28

                              MKS INSTRUMENTS, INC.

                           Technology for Productivity

       [MKS LOGO]
Technology for Productivity

     -           ASTeX(R)
     -           Baratron(R)
     -           D.I.P.(TM)
     -           HPS(R)
     -           Mass-Flo(R)
     -           On-Line(TM)
     -           Spectra(TM)
     -           ENI


OTHER IMPORTANT INFORMATION:

Investors and stockholders are urged to read the proxy statement, which will be
filed with the Securities and Exchange Commission by MKS, because it will
contain important information. The proxy statement (when it is available) will
be sent to stockholders of MKS seeking their approval of the proposed
transaction. A free copy of the proxy statement (when it is available) and other
documents filed by MKS with the Commission are available for free at the
Commission's web site at www.sec.gov. MKS stockholders may also obtain the proxy
statement and these other documents without charge by directing a request to:
Ronald C. Weigner, Vice President and Chief Financial Officer, MKS Instruments,
Inc. Six Shattuck Road, Andover, Massachusetts, 01810, telephone: (978)
975-2350. MKS and its directors, executive officers, employees and certain other
persons may be deemed to be participants in the solicitation of proxies from
MKS' stockholders to approve the proposed transaction. Such individuals may have
interests in the proposed business combination transaction, including as a
result of holding options or shares of the companies. A detailed list of the
names, affiliations and interests of the participants in the solicitation will
be contained in MKS' proxy statement to be filed with the Commission with
respect to the proposed business combination transaction.

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