Document:

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                                                                    EXHIBIT 10.4

                                RSA SECURITY INC.

                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

1.    Restatement, Purpose

      (a) Restatement. This Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan (the "Plan") of RSA Security Inc., a Delaware corporation (the
"Company"), amends and restates the 1998 Non-Officer Employee Stock Incentive
Plan of the Company initially approved by the Company's Board of Directors on
December 9, 1998 and subsequently amended.

      (b) Purpose. The purpose of the Plan is to advance the interests of the
Company's stockholders by enhancing the Company's ability to attract, retain and
motivate persons who make (or are expected to make) important contributions to
the Company by providing such persons with equity ownership opportunities and
performance-based incentives and thereby better aligning the interests of such
persons with those of the Company's stockholders. Except where the context
otherwise requires, the term "Company" shall include any of the Company's
present or future subsidiary corporations as defined in Section 424(f) of the
Internal Revenue Code of 1986, as amended, and any regulations promulgated
thereunder (the "Code").

2.    Eligibility

      All of the Company's employees (and any individuals who have accepted an
offer for employment), consultants and advisors, other than those who are also
officers (within the meaning of Section 16 of the Securities Exchange Act, as
amended (the "Exchange Act"), and the rules and regulations promulgated
thereunder) or directors of the Company, are eligible to be granted options,
restricted stock awards, or other stock-based awards (each, an "Award") under
the Plan. Each person who has been granted an Award under the Plan shall be
deemed a "Participant."

3.    Administration, Delegation

      (a) Administration by Board of Directors. The Plan will be administered by
the Board of Directors of the Company (the "Board"). The Board shall have
authority to grant Awards and to adopt, amend and repeal such administrative
rules, guidelines and practices relating to the Plan as it shall deem advisable.
The Board may correct any defect, supply any omission or reconcile any
inconsistency in the Plan or any Award in the manner and to the extent it shall
deem expedient to carry the Plan into effect and it shall be the sole and final
judge of such expediency. All decisions by the Board shall be made in the
Board's sole discretion and shall be final and binding on all persons having or
claiming any interest in the Plan or in any Award. No director or person acting
pursuant to the authority delegated by the Board shall be liable for any action
or determination relating to or under the Plan made in good faith.

      (b) Delegation to Executive Officers. To the extent permitted by
applicable law, the Board may delegate to one or more executive officers of the
Company the power to make Awards and exercise such other powers under the Plan
as the Board may determine, provided

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that the Board shall fix the maximum number of shares subject to Awards and the
maximum number of shares for any one Participant to be made by such executive
officers.

      (c) Appointment of Committees. To the extent permitted by applicable law,
the Board may delegate any or all of its powers under the Plan to one or more
committees or subcommittees of the Board (a "Committee"). All references in the
Plan to the "Board" shall mean the Board or a Committee of the Board or the
executive officer referred to in Section 3(b) to the extent that the Board's
powers or authority under the Plan have been delegated to such Committee or
executive officer.

4.    Stock Available for Awards

      Subject to adjustment under Section 8, Awards may be made under the Plan
for up to 4,760,959 shares of common stock, $.01 par value per share, of the
Company (the "Common Stock"). If any Award expires or is terminated, surrendered
or canceled without having been fully exercised or is forfeited in whole or in
part or results in any Common Stock not being issued, the unused Common Stock
covered by such Award shall again be available for the grant of Awards under the
Plan. Shares issued under the Plan may consist in whole or in part of authorized
but unissued shares or treasury shares.

5.    Nonstatutory Stock Options

      (a) General. The Board may grant nonstatutory stock options to purchase
Common Stock (each, an "Option") and determine the number of shares of Common
Stock to be covered by each Option, the exercise price of each Option and the
conditions and limitations applicable to the exercise of each Option, including
conditions relating to applicable federal or state securities laws, as it
considers necessary or advisable. No Option granted under the Plan shall be
intended to be an "incentive stock option" as defined in Section 422 of the
Code.

      (b) Exercise Price. The Board shall establish the exercise price at the
time each Option is granted and specify it in the applicable option agreement.

      (c) Duration of Options. Each Option shall be exercisable at such times
and subject to such terms and conditions as the Board may specify in the
applicable option agreement; provided that Options may not be granted for a term
in excess of ten years.

      (d) Exercise of Option. Options may be exercised by delivery to the
Company of a written notice of exercise signed by the proper person or by any
other form of notice (including electronic notice) approved by the Board
together with payment in full as specified in Section 5(e) for the number of
shares for which the Option is exercised.

      (e) Payment Upon Exercise. Common Stock purchased upon the exercise of an
Option granted under the Plan shall be paid for as follows:

            (1) in cash or by check, payable to the order of the Company;

            (2) except as the Board may, in its sole discretion, otherwise
provide in an option agreement, by (i) delivery of an irrevocable and
unconditional undertaking by a creditworthy broker to deliver promptly to the
Company sufficient funds to pay the exercise price

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or (ii) delivery by the Participant to the Company of a copy of irrevocable and
unconditional instructions to a creditworthy broker to deliver promptly to the
Company cash or a check sufficient to pay the exercise price;

            (3) to the extent permitted by the Board, in its sole discretion, by
delivery of shares of Common Stock owned by the Participant valued at their fair
market value as determined by (or in a manner approved by) the Board in good
faith ("Fair Market Value"), provided (i) such method of payment is then
permitted under applicable law and (ii) such Common Stock was owned by the
Participant at least six months prior to such delivery;

            (4) to the extent permitted by the Board, in its sole discretion, by
(i) delivery of a promissory note of the Participant to the Company on terms
determined by the Board, or (ii) payment of such other lawful consideration as
the Board may determine; or

            (5) by any combination of the above-permitted forms of payment.

      (f) Deferral. Any Participant who is a participant in a deferred
compensation plan established by the Company may elect with the permission of
the Board and in accordance with rules established by the Board to defer the
receipt of any shares of Common Stock issuable upon the exercise of an Option
provided that such election is irrevocable and made at least that number of days
prior to the exercise of the Option which shall be determined by the Board. The
Participant's account under such deferred compensation plan shall be credited
with a number of stock units equal to the number of shares so deferred.

6.    Restricted Stock

      (a) Grants. The Board may grant Awards entitling recipients to acquire
shares of Common Stock, subject to the right of the Company to repurchase all or
part of such shares at their issue price or other stated or formula price (or to
require forfeiture of such shares if issued at no cost) from the recipient in
the event that conditions specified by the Board in the applicable Award are not
satisfied prior to the end of the applicable restriction period or periods
established by the Board for such Award (each, a "Restricted Stock Award").

      (b) Terms and Conditions. The Board shall determine the terms and
conditions of any such Restricted Stock Award, including the conditions for
repurchase (or forfeiture) and the issue price, if any. Any stock certificates
issued in respect of a Restricted Stock Award shall be registered in the name of
the Participant and, unless otherwise determined by the Board, deposited by the
Participant, together with a stock power endorsed in blank, with the Company (or
its designee). At the expiration of the applicable restriction periods, the
Company (or such designee) shall deliver the certificates no longer subject to
such restrictions to the Participant or if the Participant has died, to the
beneficiary designated, in a manner determined by the Board, by a Participant to
receive amounts due or exercise rights of the Participant in the event of the
Participant's death (the "Designated Beneficiary"). In the absence of an
effective designation by a Participant, Designated Beneficiary shall mean the
Participant's estate.

7.    Other Stock-Based Awards

      The Board shall have the right to grant other Awards based upon the Common
Stock having such terms and conditions as the Board may determine, including the
grant of shares

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based upon certain conditions, the grant of securities
convertible into Common Stock and the grant of stock appreciation rights.

8.    Adjustments for Changes in Common Stock and Certain Other Events

      (a) Changes in Capitalization. In the event of any stock split, reverse
stock split, stock dividend, recapitalization, combination of shares,
reclassification of shares, spin-off or other similar change in capitalization
or event, or any distribution to holders of Common Stock other than a normal
cash dividend, (i) the number and class of securities available under this Plan,
(ii) the number and class of securities and exercise price per share subject to
each outstanding Option, (iii) the repurchase price per share subject to each
outstanding Restricted Stock Award, and (iv) the terms of each other outstanding
Award shall be appropriately adjusted by the Company (or substituted Awards may
be made, if applicable) to the extent the Board shall determine, in good faith,
that such an adjustment (or substitution) is necessary and appropriate. If this
Section 8(a) applies and Section 8(c) also applies to any event, Section 8(c)
shall be applicable to such event, and this Section 8(a) shall not be
applicable.

      (b) Liquidation or Dissolution. In the event of a proposed liquidation or
dissolution of the Company, the Board shall upon written notice to the
Participants provide that all then-unexercised Options will (i) become
exercisable in full as of a specified time at least ten business days prior to
the effective date of such liquidation or dissolution and (ii) terminate
effective upon such liquidation or dissolution, except to the extent exercised
before such effective date. The Board may specify the effect of a liquidation or
dissolution on any Restricted Stock Award or other Award granted under the Plan
at the time of the grant of such Award.

      (c) Acquisition Events

            (1) Definition. An "Acquisition Event" shall mean: (a) any merger or
consolidation of the Company with or into another entity as a result of which
the Common Stock is converted into or exchanged for the right to receive cash,
securities or other property or (b) any exchange of shares of the Company for
cash, securities or other property pursuant to a statutory share exchange
transaction.

            (2) Consequences of an Acquisition Event on Options. Upon the
occurrence of an Acquisition Event, or the execution by the Company of any
agreement with respect to an Acquisition Event, the Board may take any one or
more of the following actions:

            (i)   provide that outstanding Options shall be assumed, or
                  equivalent options shall be substituted, by the acquiring or
                  succeeding corporation (or an affiliate thereof);

            (ii)  upon written notice to the Participants, provide that all then
                  unexercised Options will become exercisable in full as of a
                  specified time prior to the Acquisition Event and will
                  terminate immediately prior to the consummation of such
                  Acquisition Event, except to the extent exercised by the
                  Participants before the consummation of such Acquisition
                  Event;

            (iii) in the event of an Acquisition Event under the terms of which
                  holders of Common Stock will receive upon consummation thereof
                  a cash payment

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                  for each share of Common Stock surrendered pursuant to such
                  Acquisition Event (the "Acquisition Price"), provide that all
                  outstanding Options shall terminate upon consummation of such
                  Acquisition Event and each Participant shall receive, in
                  exchange therefor, a cash payment equal to the amount (if any)
                  by which (A) the Acquisition Price multiplied by the number of
                  shares of Common Stock subject to such outstanding Options (to
                  the extent then exercisable), exceeds (B) the aggregate
                  exercise price of such Options; and

            (iv)  provide that all or any outstanding Options shall become
                  exercisable in full immediately prior to such event.

            (3) Consequences of an Acquisition Event on Restricted Stock Awards.
Upon the occurrence of an Acquisition Event, the repurchase and other rights of
the Company under each outstanding Restricted Stock Award shall inure to the
benefit of the Company's successor and shall apply to the cash, securities or
other property which the Common Stock was converted into or exchanged for
pursuant to such Acquisition Event in the same manner and to the same extent as
they applied to the Common Stock subject to such Restricted Stock Award.

            (4) Consequences of an Acquisition Event on Other Awards. The Board
shall specify the effect of an Acquisition Event on any other Award granted
under the Plan at the time of the grant of such Award.

9.    General Provisions Applicable to Awards

      (a) Transferability of Awards. Except as the Board may otherwise determine
or provide in an Award, Awards shall not be sold, assigned, transferred, pledged
or otherwise encumbered by the person to whom they are granted, either
voluntarily or by operation of law, except by will or the laws of descent and
distribution, and, during the life of the Participant, shall be exercisable only
by the Participant. References to a Participant, to the extent relevant in the
context, shall include references to authorized transferees.

      (b) Documentation. Each Award shall be evidenced by a written instrument
in such form as the Board shall determine. Each Award may contain terms and
conditions in addition to those set forth in the Plan.

      (c) Board Discretion. Except as otherwise provided by the Plan, each Award
may be made alone or in addition or in relation to any other Award. The terms of
each Award need not be identical, and the Board need not treat Participants
uniformly.

      (d) Termination of Status. The Board shall determine the effect on an
Award of the disability, death, retirement, authorized leave of absence or other
change in the employment or other status of a Participant and the extent to
which, and the period during which, the Participant, the Participant's legal
representative, conservator, guardian or Designated Beneficiary may exercise
rights under the Award.

      (e) Withholding. Each Participant shall pay to the Company, or make
provision satisfactory to the Board for payment of, any taxes required by law to
be withheld in connection with Awards to such Participant no later than the date
of the event creating the tax liability.

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Except as the Board may otherwise provide in an Award, when the Common Stock is
registered under the Exchange Act, Participants may, to the extent then
permitted under applicable law, satisfy such tax obligations in whole or in part
by delivery of shares of Common Stock, including shares retained from the Award
creating the tax obligation, valued at their Fair Market Value. The Company may,
to the extent permitted by law, deduct any such tax obligations from any payment
of any kind otherwise due to a Participant.

      (f) Amendment of Award. The Board may amend, modify or terminate any
outstanding Award, including but not limited to, substituting therefor another
Award of the same or a different type and changing the date of exercise or
realization, provided that the Participant's consent to such action shall be
required unless the Board determines that the action, taking into account any
related action, would not materially and adversely affect the Participant.
Without intending to limit the generality of the preceding sentence, the Board
may, without amending the Plan, modify Awards granted to Participants who are
foreign nationals or employed outside the United States to reorganize
differences in laws, rules, regulations or customers of such foreign
jurisdiction with respect to tax, securities, currency, employee benefits or
other matters.

      (g) Conditions on Delivery of Stock. The Company will not be obligated to
deliver any shares of Common Stock pursuant to the Plan or to remove
restrictions from shares previously delivered under the Plan until (i) all
conditions of the Award have been met or removed to the satisfaction of the
Company, (ii) in the opinion of the Company's counsel, all other legal matters
in connection with the issuance and delivery of such shares have been satisfied,
including any applicable securities laws and any applicable stock exchange or
stock market rules and regulations, and (iii) the Participant has executed and
delivered to the Company such representations or agreements as the Company may
consider appropriate to satisfy the requirements of any applicable laws, rules
or regulations.

      (h) Acceleration. The Board may at any time provide that any Options shall
become immediately exercisable in full or in part, that any Restricted Stock
Awards shall be free of restrictions in full or in part or that any other Awards
may become exercisable in full or in part or free of some or all restrictions or
conditions, or otherwise realizable in full or in part, as the case may be.

10.   Miscellaneous

      (a) No Right To Employment or Other Status. No person shall have any claim
or right to be granted an Award, and the grant of an Award shall not be
construed as giving a Participant the right to continued employment or any other
relationship with the Company. The Company expressly reserves the right at any
time to dismiss or otherwise terminate its relationship with a Participant free
from any liability or claim under the Plan, except as expressly provided in the
applicable Award.

      (b) No Rights As Stockholder. Subject to the provisions of the applicable
Award, no Participant or Designated Beneficiary shall have any rights as a
stockholder with respect to any shares of Common Stock to be distributed with
respect to an Award until becoming the record holder of such shares.
Notwithstanding the foregoing, in the event the Company effects a split of the
Common Stock by means of a stock dividend and the exercise price of and the
number of shares subject to such Option are adjusted as of the date of the
distribution of the dividend (rather

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than as of the record date for such dividend), then an optionee who exercises an
Option between the record date and the distribution date for such stock dividend
shall be entitled to receive, on the distribution date, the stock dividend with
respect to the shares of Common Stock acquired upon such Option exercise,
notwithstanding the fact that such shares were not outstanding as of the close
of business on the record date for such stock dividend.

      (c) Effective Date and Term of Plan. The Plan is effective as of December
9, 1998, the date on which it was adopted by the Board (the "Effective Date").
No Awards shall be granted under the Plan after the completion of ten years from
the Effective Date, but Awards previously granted may extend beyond that date.

      (d) Amendment of Plan. The Board may amend, suspend or terminate the Plan
or any portion thereof at any time.

      (e) Governing Law. The provisions of the Plan and all Awards made
hereunder shall be governed by and interpreted in accordance with the laws of
the State of Delaware, without regard to any applicable conflicts of law.

                                   Adopted by the Board of Directors on
                                   December 9, 1998

                                   Amended and restated by the Board of
                                   Directors on February 8, 2000

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                                RSA SECURITY INC.

                                 AMENDMENT NO. 1
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan (the "Plan") is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 5,064,731 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                         Adopted by the Board of Directors on
                                         April 12, 2000

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                                RSA SECURITY INC.

                                 AMENDMENT NO. 2
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 6,921,581 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                         Adopted by the Board of Directors on
                                         May 17, 2000

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 3
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 8,021,581 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                          Adopted by the Board of Directors on
                                          July 12, 2000

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 4
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 8,571,581 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                          Adopted by the Board of Directors on
                                          November 30, 2000

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 5
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 9,571,581 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                          Adopted by the Board of Directors on
                                          January 17, 2001

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 6
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 13,375,176 shares of common stock,
                  $.01 par value per share, of the Company (the "Common
                  Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                          Adopted by the Board of Directors on
                                          March 8, 2001

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 7
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      The RSA Security Inc. Amended and Restated 1998 Non-Officer Employee Stock
Incentive Plan, as amended (the "Plan"), is hereby amended as set forth below:

            1.    Section 4 of the Plan is hereby amended by deleting the first
                  sentence thereof and substituting the following therefor:

                  "Subject to adjustment under Section 8, Awards may be made
                  under the Plan for up to 21,062,764 shares (after giving
                  effect to the Company's three-for-two stock split effected as
                  a dividend on the Common Stock in March 2001) of the Company's
                  common stock, $.01 par value per share (the "Common Stock")."

            2.    In all other respects, the Plan shall remain in full force and
                  effect.

                                          Adopted by the Board of Directors on
                                          December 5, 2001

<PAGE>

                                RSA SECURITY INC.

                                 AMENDMENT NO. 8
                                       TO
                              AMENDED AND RESTATED
                 1998 NON-OFFICER EMPLOYEE STOCK INCENTIVE PLAN

      On January 26, 2005, the Company's Board of Directors resolved that if the
Company's stockholders approved the Company's new 2005 Stock Incentive Plan at
the 2005 Annual Meeting of Stockholders on May 26, 2005, then the RSA Security
Inc. Amended and Restated 1998 Non-Officer Employee Stock Incentive Plan, as
amended (the "Plan"), would be amended effective as of the date of the Annual
Meeting (1) to reduce the number of shares of Common Stock available for future
grant under the Plan to 100,000 shares (plus shares that may become available
after May 26, 2005 due to the expiration or termination of outstanding stock
options) and (2) to eliminate the Company's ability to grant any awards other
than stock options and stock appreciation rights under the Plan. On May 26,
2005, the Company's stockholders approved the 2005 Stock Incentive Plan.

      Therefore, effective May 26, 2005, the Plan is amended as set forth below:

      1.    Section 2 of the Plan is hereby deleted in its entirety and replaced
            with the following:

            "2.   Eligibility

                  "All of the Company's employees (and any individuals who have
            accepted an offer for employment), consultants and advisors, other
            than those who are also officers (within the meaning of Section 16
            of the Securities Exchange Act, as amended (the "Exchange Act"), and
            the rules and regulations promulgated thereunder) or directors of
            the Company, are eligible to be granted options or stock
            appreciation rights (each, an "Award") under the Plan. Each person
            who has been granted an Award under the Plan is deemed a
            "Participant.""

      2.    Section 4 of the Plan is hereby amended by deleting the first
            sentence thereof and replacing it with the following:

            "Subject to adjustment under Section 8, Awards may be made under the
            Plan for up to 10,608,263 shares of the Company's common stock, $.01
            par value per share (the "Common Stock") (10,508,263 of which shares
            are subject to outstanding options as of May 26, 2005)."

      3.    Section 6 of the Plan is hereby deleted in its entirety and replaced
            with the following:

            "6.   Intentionally Omitted"

<PAGE>

      4.    Section 7 of the Plan is hereby deleted in its entirety and replaced
            with the following:

            "7.   Stock Appreciation Rights

                  "The Board has the right to grant stock appreciation rights
            based upon the Common Stock having such terms and conditions as the
            Board may determine."

      5.    Section 8(a) of the Plan is hereby amended by deleting subsection
            (iii) thereof and changing the number of subsection (iv) to (iii).

      6.    Section 8(b) of the Plan is hereby amended by deleting the last
            sentence thereof and replacing it with the following:

            "The Board may specify the effect of a liquidation or dissolution on
            any other Award granted under the Plan at the time of the grant of
            such Award."

      7.    Section 8(c) of the Plan is hereby amended by deleting subsection
            (3) thereof and changing the number of subsection (4) to (3).

      8.    Section 9(h) of the Plan is hereby deleted in its entirety and
            replaced with the following:

            "(h) Acceleration. The Board may at any time provide that any
            Options shall become immediately exercisable in full or in part or
            that any other Awards may become exercisable in full or in part or
            free of some or all restrictions or conditions, or otherwise
            realizable in full or in part, as the case may be."

      9.    Except as set forth in this Amendment No. 8, the Plan remains
            unchanged and in full force and effect.

                                          Adopted by the Board of Directors on
                                          January 26, 2005<PAGE>

                                                                    EXHIBIT 10.1

                              MKS INSTRUMENTS, INC.

                           Performance Stock Agreement
           Granted Under the Second Restated 1995 Stock Incentive Plan

      AGREEMENT made this ____ day of___ ____, between MKS Instruments, Inc., a
Massachusetts corporation (the "Company"), and ______ (the "Participant").

      For valuable consideration, receipt of which is acknowledged, the parties
hereto agree as follows:

      1. Issuance of Shares.

      The Company shall issue to the Participant, subject to the terms and
conditions set forth in this Agreement and in the Company's Second Restated 1995
Stock Incentive Plan (the "Plan"), up to [_____] shares (the "Shares") of common
stock, no par value, of the Company ("Common Stock"). This Agreement shall
evidence Participant's ownership of the Shares, and Participant acknowledges
that he/she will not receive a stock certificate representing the Shares. The
Participant agrees that the Shares shall be subject to forfeiture as set forth
in Section 2 of this Agreement and the restrictions on transfer set forth in
Section 3 of this Agreement. The Company or [broker] (or such other broker with
which the Company has established a relationship) ("[Broker]") shall retain
custody of the Shares until the Shares have vested in accordance with Section 2
of this Agreement. Upon vesting of the Shares, the Company shall instruct its
transfer agent to deposit the Vested Shares (as defined in Section 2(a) below)
into the Participant's existing stock option account at [Broker] (the
"Account"), subject to payment (through sale of a portion of the Shares in
accordance with Section 6) of all applicable withholding taxes.

      2. Forfeiture.

            (a) Definitions. "Forfeiture" shall mean any forfeiture of Shares
pursuant to Sections 2(b) or 2(c) below. "Unvested Shares" shall mean all Shares
that remain subject to Forfeiture pursuant to either Section 2(b) or 2(c) below
and "Vested Shares" shall mean all Shares that are no longer subject to any
Forfeiture. "Contingent Shares" shall mean those shares that are no longer
subject to Forfeiture pursuant to the terms of Section 2(b) below, but remain
subject to Forfeiture pursuant to Section 2(c) below. "Vesting Date" shall mean
the date that all Forfeiture provision lapses with respect to any Shares (or the
first business day thereafter if such date falls on a day when the market is
closed). For purposes of this Agreement, "employ" or "employment" with the
Company shall include employment with a parent or subsidiary of the Company.

            (b) Performance Vesting. As set forth in the chart below, based upon
the way that the Company's actual annual pro forma(1) earnings per share for the
year ending December 31, [generally, the year following grant year] (the "20__
Actual EPS") relate to the Company's

----------------
(1) Excludes certain non-operating items, as determined by the Company

<PAGE>

internal target for 20__ annual pro forma earnings per share, [may be
established at a future date] (the "20__ Target EPS"), then all Shares that are
not Contingent Shares (as defined below) shall be automatically forfeited to the
Company, effective as of the date of the Company's public announcement of the
20__ Actual EPS.

<TABLE>
<CAPTION>
     IF THE 20__               "CONTINGENT
   ACTUAL EPS IS:          SHARES"(2) SHALL MEAN:                              EXAMPLE
---------------------   --------------------------   ------------------------------------------------------------
<S>                     <C>                          <C>
Less than 50% of 20__            0 shares            IF:  Company's 20__ Actual EPS is 40% of 20__ Target EPS.
Target EPS

                                                     THEN: No shares are Contingent Shares.

50% to 100% of 20__      [_____] Shares multiplied   IF: Company's 20__ Actual EPS is 60% of 20__ Target EPS.
Target EPS              by the percentage that the
                         20__ Actual EPS bears to    THEN: [_____] shares (60% x [_____]) are Contingent Shares.
                            the 20__ Target EPS

More than 100% of           (1) [_____] Shares                                Example #1
20__ Target EPS
                                   plus              IF: Company's 20__ Actual EPS is 140% of 20__ Target EPS.

                          (2) (a) [_____] Shares     THEN: [_____] shares are Contingent Shares, calculated as
                           multiplied by (b) the     follows: (1) [_____] shares, plus (2) [_____] shares
                          percentage by which the    (which is 40% x [_____] shares).
                          20__ Actual EPS exceeds
                              100% of the 20__
                                Target EPS                                   Example #2

                             (up to a maximum        IF: Company's 20__ Actual EPS is 180% of 20__ Target EPS.
                           aggregate of [_____]
                                 shares)             THEN: [_____] shares are Contingent Shares, calculated as
                                                     follows:  (1) [_____] shares, plus (2) [_____] shares
                                                     (which is 80% x [_____] shares).
</TABLE>

Contingent Shares shall remain "Unvested Shares" pursuant to this Agreement
until the Contingent Shares are no longer subject to Forfeiture pursuant to
Section 2(c) below.

            (c) Vesting Period. In addition to any forfeiture pursuant to
Section 2(b) above, in the event that Participant ceases to be employed by the
Company for any reason or no reason (except for death or disability), with or
without cause, prior to [third anniversary from

----------------
(2) Any fractional shares shall be rounded up to the next whole share. Maximum
number of Contingent Shares is [maximum number granted per Section 1].

                                       2
<PAGE>

date of grant], then effective at the time of such cessation, all remaining
Shares shall automatically be forfeited to the Company. In the event that the
Participant ceases to be employed by the Company by reason of death or
disability prior to [third anniversary from date of grant], then, that
percentage of the Shares that had not been previously Forfeited pursuant to
Section 2(a) prior to the time of such death or disability, that is equal to
percentage of the period of time between the date of this Agreement and [third
anniversary from date of grant], that is remaining at the time of such death or
disability, shall automatically be forfeited to the Company. For the purpose of
this Section 2, "disability" shall mean disability as defined in Section
216(i)(1) of the Social Security Act.

            (d) Change in Control. Notwithstanding the foregoing, if, prior to
[third anniversary from date of grant], and within two years of the
effectiveness of a Change in Control (as defined below), the Participant is (i)
terminated by the Company without Cause (as defined below) or (ii) terminates
his employment for Good Reason (as defined below), then, 100% of the
Participants Unvested Shares shall immediately become Vested Shares and shall no
longer be subject to the Forfeiture provisions under this Agreement. For
purposes of this section "Change in Control" means the first to occur of any of
the following events: (I) any "person" (as that term is used in Section 13 and
14(d)(2) of the Securities Exchange Act of 1934 ("Exchange Act")) becomes the
beneficial owner (as that term is used in Section 13(d) of the Exchange Act),
directly or indirectly, of fifty percent (50%) or more of the Company's capital
stock entitled to vote in the election of directors; (II) the shareholders of
the Company approve any consolidation or merger of the Company, other than a
consolidation or merger of the Company in which the holders of the common stock
of the Company immediately prior to the consolidation or merger hold more than
fifty percent (50%) of the common stock of the surviving corporation immediately
after the consolidation or merger; or (III) the shareholders of the Company
approve the sale or transfer of all or substantially all of the assets of the
Company to parties that are not within a "controlled group of corporations" (as
defined in Code Section 1563) in which the Company is a member. For purposes of
this Agreement, "Cause" shall mean conviction for the commission of a felony,
willful failure by the Participant to perform his responsibilities to the
Company, or willful misconduct by the Employee. For purposes of this section,
"Good Reason" shall mean termination of Participant's employment by Participant
within 90 days following (I) a material diminution in Participant's positions,
duties and responsibilities from those described in this Employment Agreement,
(II) a material reduction in Participant's base salary (other than a reduction
which is part of a general salary reduction program affecting senior executives
of the Company), (III) a material reduction in the aggregate value of the
pension and welfare benefits provided to Participant from those in effect prior
to the Change in Control (other than a reduction which is proportionate to the
reductions applicable to other senior executives pursuant to a cost-saving plan
that includes all senior executives), (IV) a material breach of any provision of
this Employment Agreement by the Company or (V) the Company's requiring
Participant to be based at a location that creates for Participant a one way
commute in excess of 60 miles from his primary residence, except for required
travel on the Company's business to an extent substantially consistent with the
business travel obligations of Participant under this Employment Agreement.
Notwithstanding the foregoing, a termination shall not be treated as a
termination for Good Reason (I) if Participant shall have consented in writing
to the occurrence of the event giving rise to the claim of termination for Good
Reason or (II) unless Participant shall have delivered a written notice to the
Company within 30 days of his having actual knowledge of the

                                       3
<PAGE>

occurrence of one of such events stating that he intends to terminate his
employment for Good Reason and specifying the factual basis for such
termination, and such event, if capable of being cured, shall not have been
cured within 30 days of the receipt of such notice.

            (e) Notice. Within 90 days after any Forfeiture, the Company shall
provide the Participant (or his estate) a written notice of forfeiture,
specifying the number of Shares forfeited. Failure to provide such notice on a
timely basis shall have no effect on the Forfeiture of the Shares.

      3. Restrictions on Transfer.

      The Participant shall not sell, assign, transfer, pledge, hypothecate or
otherwise dispose of, by operation of law or otherwise (collectively "transfer")
any Unvested Shares, or any interest therein, except that the Participant may
transfer such Unvested Shares (i) to or for the benefit of any spouse, children,
parents, uncles, aunts, siblings, grandchildren and any other relatives approved
by the Board of Directors (collectively, "Approved Relatives") or to a trust
established solely for the benefit of the Participant and/or Approved Relatives,
provided that such Unvested Shares shall remain subject to this Agreement
(including without limitation the terms of Forfeiture and the restrictions on
transfer set forth in this Section 3) and such permitted transferee shall, as a
condition to such transfer, deliver to the Company a written instrument
confirming that such transferee shall be bound by all of the terms and
conditions of this Agreement or (ii) as part of the sale of all or substantially
all of the shares of capital stock of the Company (including pursuant to a
merger or consolidation), provided that, in accordance with the Plan, the
securities or other property received by the Participant in connection with such
transaction shall remain subject to this Agreement.

      4. Restrictive Legends.

      All certificates representing Shares shall have affixed thereto a legend
in substantially the following form, in addition to any other legends that may
be required under federal or state securities laws:

            "The shares of stock represented by this certificate are subject to
            restrictions on transfer and to forfeiture as set forth in a certain
            Performance Stock Agreement between the corporation and the
            registered owner of these shares (or his predecessor in interest),
            and such Agreement is available for inspection without charge at the
            office of the Secretary of the corporation."

      5. Provisions of the Plan.

            (a) This Agreement is subject to the provisions of the Plan, a copy
of which is furnished to the Participant with this Agreement.

            (b) Upon the occurrence of a merger of, or acquisition of, the
Company, the Forfeiture provision and other rights of the Company hereunder
shall inure to the benefit of any successor to the Company.

                                       4
<PAGE>

      6. Withholding Taxes; Section 83(b) Election.

            (a) The Company's obligation to deliver Shares to Participant upon
the vesting of such shares shall be subject to the satisfaction of all
applicable federal, state and local income and employment tax withholding
requirements ("Withholding Taxes"). In order to satisfy all Withholding Taxes
due upon vesting of Participant's Shares, Participant agrees to the following:

            (b) As a condition to receiving any Vested Shares, on the date of
this Agreement, Participant must execute the Irrevocable Standing Order to Sell
Shares attached hereto, which authorizes the Company and [Broker] to take the
actions described in this subsection 6(b) (the "Standing Order"). Participant
authorizes [Broker] to sell, at the market price and on the applicable Vesting
Date the number of Vested Shares that the Company has instructed [Broker] is
necessary to obtain proceeds sufficient to satisfy the Withholding Taxes.
Participant understands and agrees that the number of Vested Shares that
[Broker] will sell will be based on the closing price of the Common Stock on the
last trading day before the Vesting Date. The Participant agrees to execute and
deliver such documents, instruments and certificates as may reasonably be
required in connection with the sale of the Vested Shares pursuant to this
Section 6.

            (c) Participant agrees that the proceeds received from the sale of
Vested Shares pursuant to Section 6(b) will be used to satisfy the Withholding
Taxes and, accordingly, Participant hereby authorizes [Broker] to pay such
proceeds to the Company for such purpose. Participant understands that to the
extent that the proceeds obtained by such sale exceed the amount necessary to
satisfy the Withholding Taxes, such excess proceeds shall be deposited into the
Account. Participant further understands that any remaining Vested Shares shall
be deposited into the Account.

            (d) Participant acknowledges and agrees that, in the event that
there is not a market in the Common Stock, the Company will have the right to
make other arrangements to satisfy the Withholding Taxes due upon vesting of
Participant's Shares, including, but not limited to, the right to deduct amounts
from payments of any kind otherwise due to the Participant.

            (e) The Participant has reviewed with the Participant's own tax
advisors the federal, state, local and foreign tax consequences of this
investment and the transactions contemplated by this Agreement. The Participant
is relying solely on such advisors and not on any statements or representations
of the Company or any of its agents. The Participant understands that the
Participant (and not the Company) shall be responsible for the Participant's own
tax liability that may arise as a result of this investment or the transactions
contemplated by this Agreement. The Participant understands that it may be
beneficial in many circumstances to elect to be taxed at the time the Shares are
issued rather than when and as the Forfeiture provisions lapse by filing an
election under Section 83(b) of the Code with the I.R.S. within 30 days from the
date of purchase. THE PARTICIPANT ACKNOWLEDGES THAT IT IS THE PARTICIPANT'S SOLE
RESPONSIBILITY AND NOT THE COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION
83(b), EVEN IF THE PARTICIPANT

                                       5
<PAGE>

REQUESTS THE COMPANY OR ITS REPRESENTATIVES TO MAKE THIS FILING ON THE
PARTICIPANT'S BEHALF.

            (f) The Participant represents to the Company that, as of the date
hereof, he is not aware of any material nonpublic information about the Company
or the Common Stock. The Participant and the Company have structured this
Agreement to constitute a "binding contract" relating to the sale of Common
Stock pursuant to this Section 5, consistent with the affirmative defense to
liability under Section 10(b) of the Securities Exchange Act of 1934 under Rule
10b5-1(c) promulgated under such Act.

      7. Miscellaneous.

            (a) No Rights to Employment. The Participant acknowledges and agrees
that the vesting of the Shares pursuant to Section 2 hereof is earned only in
accordance with the terms of such section. The Participant further acknowledges
and agrees that the transactions contemplated hereunder and the vesting schedule
set forth herein do not constitute an express or implied promise of continued
engagement as an employee or consultant for the vesting period, for any period,
or at all.

            (b) Severability. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement, and each other provision of this
Agreement shall be severable and enforceable to the extent permitted by law.

            (c) Waiver. Any provision for the benefit of the Company contained
in this Agreement may be waived, either generally or in any particular instance,
by the Board of Directors of the Company.

            (d) Binding Effect. This Agreement shall be binding upon and inure
to the benefit of the Company and the Participant and their respective heirs,
executors, administrators, legal representatives, successors and assigns,
subject to the restrictions on transfer set forth in Sections3 and 4 of this
Agreement.

            (e) Notice. All notices required or permitted hereunder shall be in
writing and deemed effectively given upon personal delivery or five days after
deposit in the United States Post Office, by registered or certified mail,
postage prepaid, addressed to the other party hereto at the address shown
beneath his or its respective signature to this Agreement, or at such other
address or addresses as either party shall designate to the other in accordance
with this Section 7(e).

            (f) Pronouns. Whenever the context may require, any pronouns used in
this Agreement shall include the corresponding masculine, feminine or neuter
forms, and the singular form of nouns and pronouns shall include the plural, and
vice versa.

            (g) Entire Agreement. This Agreement and the Plan constitute the
entire agreement between the parties, and supersedes all prior agreements and
understandings, relating to the subject matter of this Agreement.

                                       6
<PAGE>

            (h) Amendment. This Agreement may be amended or modified only by a
written instrument executed by both the Company and the Participant.

            (i) Governing Law. This Agreement shall be construed, interpreted
and enforced in accordance with the internal laws of the State of Massachusetts
without regard to any applicable conflicts of laws.

            (j) Participant's Acknowledgments. The Participant acknowledges that
he or she: (i) has read this Agreement; (ii) has been represented in the
preparation, negotiation, and execution of this Agreement by legal counsel of
the Participant's own choice or has voluntarily declined to seek such counsel;
and (iii) understands the terms and consequences of this Agreement; and (iv) is
fully aware of the legal and binding effect of this Agreement.

      IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the day and year first above written.

                                     MKS INSTRUMENTS, INC.

                                     By:___________________________
                                     Title:_______________________
                                     90 Industrial Way
                                     Wilmington, MA 01887

                                     _________________________________
                                     [Participant's Name]

                                     Address: _________________
                                              _________________

                                       7
<PAGE>

                                                                       Exhibit A

                    IRREVOCABLE STANDING ORDER TO SELL SHARES

      I, ___________________________________, have been granted _____________
shares of performance stock by MKS Instruments, Inc. ("MKS"), which is evidenced
by a restricted stock agreement between me and MKS (the "Agreement," copy
attached). Provided that I remain employed by MKS on each vesting date, the
shares vest according to the schedule set forth in the Performance Stock
Agreement executed between me and MKS, dated [date of grant], a copy of which
has been provided to you.

      I understand that on each vesting date, the vested shares (the "Shares")
will be deposited into my account no. _____________ at [broker] ("[Broker]") and
that I will recognize taxable ordinary income as a result. Pursuant to the terms
of the Agreement and as a condition of my receipt of the Shares, I understand
and agree that, for each vesting date, I must sell a number of shares sufficient
to satisfy all withholding taxes applicable to that ordinary income. Therefore,
I HEREBY DIRECT [BROKER] TO SELL, AT THE MARKET PRICE AND ON EACH VESTING DATE
LISTED ABOVE (OR THE FIRST BUSINESS DAY THEREAFTER IF A VESTING DATE SHOULD FALL
ON A DAY WHEN THE MARKET IS CLOSED), THE NUMBER OF SHARES THAT MKS INFORMS
[BROKER] IS SUFFICIENT TO SATISFY THE APPLICABLE WITHHOLDING TAXES, WHICH SHALL
BE CALCULATED BASED ON THE CLOSING PRICE OF MKS'S COMMON STOCK ON THE LAST
TRADING DAY BEFORE EACH VESTING DATE. I understand that [Broker] will remit the
proceeds to MKS for payment of the withholding taxes.

      I hereby agree to indemnify and hold [Broker] harmless from and against
all losses, liabilities, damages, claims and expenses, including reasonable
attorneys' fees and court costs, arising out of any (i) negligent act, omission
or willful misconduct by MKS in carrying out actions pursuant to the third
sentence of the preceding paragraph and (ii) any action taken or omitted by
[Broker] in good faith reliance upon instructions herein or upon instructions or
information transmitted to [Broker] by MKS pursuant to the third sentence of the
preceding paragraph.

      I understand and agree that by signing below, I am making an Irrevocable
Standing Order to Sell Shares which will remain in effect until all of the
shares have vested. I also agree that this Irrevocable Standing Order to Sell
Shares is in addition to and subject to the terms and conditions of any existing
Account Agreement that I have with[Broker].

________________________________         _______________________________________
Signature                                Signature (Additional Account Holder)
Print name: ____________________         Print name: __________________________
Dated:  _______ __, 20__                 Dated:  ________ __, 20__

                                       8

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