Document:

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                                                                     EXHIBIT 4.1

                          CAPSTONE TURBINE CORPORATION

                     STOCK OPTION AGREEMENT WITH JOHN TUCKER

         This Stock Option Agreement with John Tucker (the "Stock Option
Agreement") is entered into as of August 1, 2003 to attract and retain Mr.
Tucker for the position of President and Chief Executive Officer of Capstone
Turbine Corporation (the "Company") to promote the success of the Company's
business. This Stock Option Agreement constitutes a plan separate from the
Capstone Turbine Corporation 2000 Equity Incentive Plan (as such plan has been
and may be amended from time to time, the "2000 Plan") for all purposes,
including with respect to the Company's filing obligations under the Securities
Act of 1933, as amended ("Securities Act") on Form S-8. Although the Option (as
defined below) granted hereunder is not granted under the 2000 Plan, it shall be
governed by terms and conditions identical to those under the 2000 Plan, as
further provided herein.

         All capitalized terms used in this Stock Option Agreement without
definition shall have the meanings ascribed to such terms in the 2000 Plan.

I.       NOTICE OF STOCK OPTION GRANT

         John Tucker
         450 Ironwood Drive
         Canonsburg, PA 15317

         You, John Tucker ("Optionee"), have been granted an option (the
"Option") to purchase shares of Common Stock of the Company, subject to the
terms and conditions of the 2000 Plan and this Stock Option Agreement. The terms
of your grant are set forth below:

          Date of Grant:                             August 1, 2003

          Vesting Commencement Date:                 August 1, 2003

          Exercise Price per Share:                  $1.18 per Share

          Total Number of Shares Granted:            2,000,000

          Total Exercise Price:                      $2,360,000

          Type of Option:                            Non-Qualified Stock Option

          Term:                                      10 years commencing on Date
                                                     of Grant

          Expiration Date:                           August 1, 2013

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         Exercise and Vesting Schedule:

         The Shares (as defined below) subject to this Option shall vest
according to the following schedule:

         Twenty-five percent (25%) of the Shares subject to the Option (rounded
down to the next whole number of shares) shall vest one year after the Date of
Grant, and 1/48th of the Shares subject to the Option (rounded down to the next
whole number of shares) shall vest each month thereafter on the date
corresponding to the Date of Grant, so that all of the Shares shall be vested on
the forty-eighth (48th) month anniversary of the Date of Grant, subject to, with
respect to each vesting date, Optionee continuing to be either an Employee or a
Consultant (as such terms are defined in the 2000 Plan) to the Company on such
vesting date; provided, however, that if Optionee is terminated by the Company
other than for Cause (as such term is defined in the 2000 Plan) prior to the
one-year anniversary of the Date of Grant, 1/48th of the Shares subject to the
Option (rounded down to the next whole number of shares) shall be deemed to have
vested on the one-month anniversary of the Date of Grant and on each monthly
anniversary thereafter until the date of such termination.

         Optionee agrees to be bound by the terms of the Option as set forth in
this Stock Option Agreement. Optionee hereby acknowledges receipt of a copy of
the official prospectus for the 2000 Plan. A copy of the 2000 Plan is available
upon request made to the Corporate Secretary at the Company's principal offices
at 21211 Nordhoff Street, Chatsworth, California 91311.

         Termination Period:

         The Option shall terminate on the Expiration Date; provided, however,
that if Optionee ceases to be either an Employee or a Consultant prior to the
Expiration Date, then the Option shall terminate earlier pursuant to Sections 5,
6, and 7 of Article II below.

II.      AGREEMENT

         1.       Grant of Option. The Company hereby grants to the Optionee an
Option to purchase the Common Stock (the "Shares") as set forth in the Notice of
Stock Option Grant in Article I above, at the exercise price per Share set forth
in the Notice of Stock Option Grant (the "Exercise Price"). Notwithstanding
anything to the contrary in this Stock Option Agreement, the Option is subject
to the terms, definitions and provisions of the 2000 Plan, which are
incorporated herein by reference.

         2.       Exercise of Option. The Option is exercisable as follows:

                  (a)      Right to Exercise.

                           (i)      The Option shall be exercisable cumulatively
according to the vesting schedule set forth in the Notice of Stock Option Grant.
For purposes of this Stock Option Agreement, Shares subject to this Option shall
vest based on Optionee's continued status as an Employee or a Consultant.

                           (ii)     The Option may not be exercised for a
fraction of a Share.

                                       2
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                           (iii)    In the event of Optionee's death, disability
or other termination of the Optionee's status as an Employee or a Consultant,
the exercisability of the Option is governed by Sections 5, 6 and 7 of this
Article II.

                           (iv)     In no event may the Option be exercised
after the Expiration Date of the Option as set forth in the Notice of Stock
Option Grant in Article I above.

                  (b)      Method of Exercise. The Option shall be exercisable
by written Notice (in the form attached as Exhibit A). The Notice must state the
number of Shares for which the Option is being exercised, and such other
representations and agreements with respect to such Shares as may be required by
the Company pursuant to the provisions of the 2000 Plan. The Notice must be
signed by the Optionee and shall be delivered in person or by certified mail to
the Corporate Secretary of the Company. The Notice must be accompanied by
payment of the Exercise Price, including payment of any applicable withholding
tax. The Option shall be deemed to be exercised upon receipt by the Company of
such written Notice accompanied by the Exercise Price and payment of any
applicable withholding tax.

                  No Shares shall be issued pursuant to the exercise of an
Option unless such issuance and such exercise comply with all relevant
provisions of law and the requirements of any stock exchange upon which the
Shares may then be listed. Assuming such compliance, for income tax purposes the
Shares shall be considered transferred to the Optionee on the date on which the
Option is exercised with respect to such Shares.

         3.       Lock-Up Period. Optionee hereby agrees that if so requested by
the Company or any representative of the underwriters (the "Managing
Underwriter") in connection with any registration of the offering of any
securities of the Company under the Securities Act or any applicable state laws,
Optionee shall not sell or otherwise transfer any Shares or other securities of
the Company during the 180-day period (or such longer period as may be requested
in writing by the Managing Underwriter and agreed to in writing by the Company)
(the "Market Standoff Period") following the effective date of a registration
statement of the Company filed under the Securities Act. The Company may impose
stop-transfer instructions with respect to securities subject to the foregoing
restrictions until the end of such Market Standoff Period.

         4.       Method of Payment. Payment of the Exercise Price shall be by
any of the following, or a combination thereof, at the election of the Optionee:

                  (a)      cash;

                  (b)      check;

                  (c)      with the consent of the Administrator, a full
recourse promissory note bearing interest (at no less than such rate as shall
then preclude the imputation of interest under the Code) and payable upon such
terms as may be prescribed by the Administrator;

                  (d)      with the consent of the Administrator, surrender of
other Shares which (A) in the case of Shares acquired from the Company, have
been owned by the Optionee for more than six (6) months on the date of
surrender, and (B) have a Fair Market Value on the date of surrender equal to
the Exercise Price of the Shares as to which the Option is being exercised;

                                       3
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                  (e)      with the consent of the Administrator, surrendered
Shares issuable upon the exercise of the Option having a Fair Market Value on
the date of exercise equal to the aggregate Exercise Price of the Option or
exercised portion thereof;

                  (f)      with the consent of the Administrator, property of
any kind which constitutes good and valuable consideration; or

                  (g)      with the consent of the Administrator, delivery of a
notice that the Optionee has placed a market sell order with a broker with
respect to Shares then issuable upon exercise of the Option and that the broker
has been directed to pay a sufficient portion of the net proceeds of the sale to
the Company in satisfaction of the aggregate Exercise Price; provided, that
payment of such proceeds is then made to the Company upon settlement of such
sale.

         5.       Termination of Relationship. If Optionee ceases to be either
an Employee or a Consultant (other than for Cause or by reason of the Optionee's
death or the total and permanent disability of the Optionee as defined in Code
Section 22(e)(3)), the Option, to the extent vested as of the date on which
Optionee ceases to be either an Employee or a Consultant, shall remain
exercisable for three (3) months from such date (but in no event later than the
Expiration Date of the term of the Option as set forth in the Notice of Stock
Option Grant). To the extent that the Option is not vested at the date on which
Optionee ceases to be either an Employee or a Consultant, or if Optionee does
not exercise the Option within the time specified herein, the Option shall
terminate. If Optionee's status as either an Employee or a Consultant is
terminated for Cause, the Option, whether vested (in whole or in part) or
unvested, shall immediately terminate.

         6.       Disability of Optionee. If Optionee ceases to be either an
Employee or a Consultant as a result of his total and permanent disability as
defined in Code Section 22(e)(3), the Option, to the extent vested as of the
date on which Optionee ceases to be either an Employee or Consultant, shall
remain exercisable for twelve (12) months from such date (but in no event later
than the Expiration Date of the term of the Option as set forth in the Notice of
Stock Option Grant). To the extent that the Option is not vested as of the date
on which Optionee ceases to be either an Employee or Consultant, or if Optionee
does not exercise such Option within the time specified herein, the Option shall
terminate.

         7.       Death of Optionee. If Optionee ceases to be either an Employee
or Consultant as a result of the Optionee's death, the Option, to the extent
vested as of the date of death, shall remain exercisable for twelve (12) months
following the date of death (but in no event later than the Expiration Date of
the term of the Option as set forth in the Notice of Stock Option Grant) by
Optionee's estate or by a person who acquires the right to exercise the Option
by bequest or inheritance. To the extent that the Option is not vested as of the
date of death, or if the Option is not exercised within the time specified
herein, the Option shall terminate.

         8.       Non-Transferability of Option. The Option may not be
transferred in any manner except by will or by the laws of descent or
distribution. It may be exercised during the lifetime of Optionee only by
Optionee. The terms of the Option shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

         9.       Term of Option. The Option may be exercised only within the
term set forth in the Notice of Stock Option Grant.

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                  This Stock Option Agreement may be executed in two or more
counterparts, each of which shall be deemed an original and all of which shall
constitute one document.

                                    CAPSTONE TURBINE CORPORATION

                                    By: /s/ KAREN CLARK
                                        ----------------------------------------

                                    Name: Karen Clark

                                    Title: Senior Vice President, Chief
                                    Financial Officer

         OPTIONEE ACKNOWLEDGES AND AGREES THAT THE VESTING OF SHARES PURSUANT TO
         THE OPTION HEREOF IS EARNED ONLY BY CONTINUING EMPLOYMENT OR
         CONSULTANCY AT THE WILL OF THE COMPANY (NOT THROUGH THE ACT OF BEING
         HIRED, BEING GRANTED THE OPTION OR ACQUIRING SHARES HEREUNDER).
         OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT NOTHING IN THIS STOCK
         OPTION AGREEMENT, NOR IN THE CAPSTONE TURBINE CORPORATION 2000 EQUITY
         INCENTIVE PLAN, WHICH IS INCORPORATED HEREIN BY REFERENCE, SHALL CONFER
         UPON OPTIONEE ANY RIGHT WITH RESPECT TO CONTINUATION OF EMPLOYMENT OR
         CONSULTANCY BY THE COMPANY, NOR SHALL IT INTERFERE IN ANY WAY WITH
         OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO TERMINATE OPTIONEE'S
         EMPLOYMENT OR CONSULTANCY AT ANY TIME, WITH OR WITHOUT CAUSE.

         Optionee acknowledges receipt of a copy of the 2000 Plan and represents
that he is familiar with the terms and provisions thereof. Optionee hereby
accepts the Option subject to all of the terms and provisions hereof. Optionee
has reviewed the 2000 Plan and this Stock Option Agreement in their entirety,
has had an opportunity to obtain the advice of counsel prior to executing this
Stock Option Agreement and fully understands all provisions of the Stock Option
Agreement and the Option granted hereunder. Optionee hereby agrees to accept as
binding, conclusive and final all decisions or interpretations of the
Administrator upon any questions arising under the 2000 Plan or the Stock Option
Agreement. Optionee further agrees to notify the Company upon any change in the
residence address indicated below.

Dated: August 1, 2003               /s/ JOHN TUCKER
                                    --------------------------------------------
                                    John Tucker, OPTIONEE

                                    Residence Address:

                                    450 Ironwood Drive
                                    Canonsburg, PA 15317

                                       5
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                                    EXHIBIT A

                          CAPSTONE TURBINE CORPORATION

                                 EXERCISE NOTICE

Capstone Turbine Corporation
21211 Nordhoff Street
Chatsworth, CA 91311

Attention: Corporate Secretary

         1.       Exercise of Option. Effective as of today, ___________, 20__,
the undersigned ("Optionee") hereby elects to exercise Optionee's option to
purchase _________ shares of the Common Stock (the "Shares") of Capstone Turbine
Corporation (the "Company") under and pursuant to the terms of that certain
Option granted to me on August 1, 2003 under the Stock Option Agreement of the
same date (the "Stock Option Agreement").

         The Stock Option Agreement constitutes a plan separate from the
Capstone Turbine Corporation 2000 Equity Incentive Plan (as such plan has been
and may be amended from time to time, the "2000 Plan") for all purposes,
including with respect to the Company's filing obligations under the Securities
Act of 1933, as amended ("Securities Act") on Form S-8. Although the Option
granted under the Stock Option Agreement is not granted under the 2000 Plan, it
shall be governed by terms and conditions identical to those under the 2000
Plan, which are incorporated into the Stock Option Agreement by reference.
Optionee agrees to be bound by the terms of the Option as set forth in the Stock
Option Agreement.

         Optionee hereby further acknowledges receipt of a copy of the official
prospectus for the 2000 Plan. A copy of the 2000 Plan is available upon request
made to the Corporate Secretary at the Company's principal offices at 21211
Nordhoff Street, Chatsworth, California 91311.

         2.       Representations of Optionee. Optionee acknowledges that
Optionee has received, read and understands the 2000 Plan and the Stock Option
Agreement. Optionee agrees to abide by and be bound by the terms and conditions
of the 2000 Plan and the Stock Option Agreement.

         3.       Rights as Stockholder. Until the stock certificate evidencing
such Shares is issued (as evidenced by the appropriate entry on the books of the
Company or of a duly authorized transfer agent of the Company), no right to vote
or receive dividends or any other rights as a stockholder shall exist with
respect to Shares subject to the Option, notwithstanding the exercise of the
Option. The Company shall issue (or cause to be issued) such stock certificate
promptly after the Option is exercised. No adjustment will be made for a
dividend or other right for which the record date is prior to the date the stock
certificate is issued, except as provided in Section 15 of the 2000 Plan.
Optionee shall enjoy rights as a stockholder until such time as Optionee
disposes of the Shares.

         4.       Tax Consultation. Optionee understands that Optionee may
suffer adverse tax consequences as a result of Optionee's purchase or
disposition of the Shares. Optionee represents that Optionee has consulted with
any tax consultants Optionee deems advisable in connection with

<PAGE>

the purchase or disposition of the Shares and that Optionee is not relying on
the Company for any tax advice.

         5.       Successors and Assigns. The Company may assign any of its
rights under this Notice to single or multiple assignees, and this Notice shall
inure to the benefit of the successors and assigns of the Company. This Notice
shall be binding upon Optionee and his heirs, executors, administrators,
successors and assigns.

         6.       Interpretation. Any dispute regarding the interpretation of
this Notice shall be submitted by Optionee or by the Company forthwith to the
Company's Board of Directors or the committee thereof that administers the 2000
Plan (the "Administrator"), which shall review such dispute at its next regular
meeting. The resolution of such a dispute by the Administrator shall be final
and binding on the Company and on Optionee.

         7.       Governing Law; Severability. This Notice shall be governed by
and construed in accordance with the laws of the State of Delaware excluding
that body of law pertaining to conflicts of law. Should any provision of this
Notice be determined by a court of law to be illegal or unenforceable, the other
provisions shall nevertheless remain effective and shall remain enforceable.

         8.       Notices. Any notice required or permitted hereunder shall be
given in writing and shall be deemed effectively given upon personal delivery or
upon deposit in the United States mail by certified mail, with postage and fees
prepaid, addressed to the other party at its address as shown below beneath its
signature, or to such other address as such party may designate in writing from
time to time to the other party.

         9.       Further Instruments. The parties agree to execute such further
instruments and to take such further action as may be reasonably necessary to
carry out the purposes and intent of this Notice.

         10.      Delivery of Payment. Optionee herewith delivers to the Company
the full Exercise Price for the Shares, as well as any applicable withholding
tax.

         11.      Entire Agreement. The 2000 Plan and the Stock Option Agreement
are incorporated herein by reference. This Notice, the 2000 Plan and the Stock
Option Agreement constitute the entire agreement of the parties and supersede in
their entirety all prior undertakings and agreements of the Company and Optionee
with respect to the subject matter hereof.

                            [Signature page follows]

<PAGE>

Submitted by:                       Accepted by:

OPTIONEE: John Tucker               CAPSTONE TURBINE CORPORATION

                                    By: ________________________________________

                                    Name: ______________________________________

                                    Title: _____________________________________

Residence Address:

450 Ironwood Drive
Canonsburg, PA 15317<PAGE>

                                                                     EXHIBIT 4.2

                          CAPSTONE TURBINE CORPORATION

                       RESTRICTED STOCK PURCHASE AGREEMENT

I.       NOTICE OF GRANT OF RESTRICTED STOCK

         NAME: JOHN TUCKER

         ADDRESS: 450 IRONWOOD DRIVE
                  CANONSBURG, PA 15317

         You have been granted a right to purchase Shares of Restricted Stock,
subject to the terms and conditions of this Agreement, as follows:

         Date of Grant                                        August 4, 2003

         Exercise Price Per Share                             $0.001

         Total Number of Shares of Restricted Stock           500,000

         Total Purchase Price                                 $500.00

         Expiration Date                                      August 31, 2003

         YOU MUST EXERCISE THIS STOCK PURCHASE RIGHT BEFORE THE EXPIRATION DATE
OR IT WILL TERMINATE AND YOU WILL HAVE NO FURTHER RIGHT TO PURCHASE THE SHARES.

II.      AGREEMENT

         1.       PURCHASE AND SALE OF SHARES. The undersigned (the "PURCHASER")
hereby purchases from the Company, and the Company hereby issues and sells to
Purchaser, an aggregate of 500,000 shares of Common Stock (as hereinafter
defined) (the "SHARES"), at a price of $0.001 per share (an aggregate purchase
price of $500.00). The Company shall, promptly after execution of this
Agreement, issue a certificate representing the Shares registered in the name of
Purchaser, which certificate shall be held in escrow pursuant to the provisions
of Section 6 hereof. In return, the Purchaser shall deliver to the Company (a)
an executed counterpart of this Agreement, and (b) the purchase price of the
Shares in the form of a check payable to the Company.

         2.       STOCK SPLITS, ETC. If, from time to time during the term of
this Agreement (i) there is any stock dividend or liquidating dividend of cash
and/or property, stock split or other change in the character or amount of any
of the outstanding securities of the Company; or (ii) there is any
consolidation, merger or sale of all, or substantially all, of the assets of the
Company, then, in such event, any and all new, substituted or additional
securities or other property to which Purchaser is entitled by reason of his
ownership of the Shares shall be immediately subject to this Agreement and

<PAGE>

be included in the word "Shares" for all purposes with the same force and effect
as the Shares presently subject to the terms of this Agreement.

         3.       DEFINITIONS. As used herein, the following definitions shall
apply:

                  (a)      "BOARD" means the Board of Directors of the Company
or any committee of the Board that has been designated by the Board to
administer this Agreement.

                  (b)      "CODE" means the Internal Revenue Code of 1986, as
amended.

                  (c)      "COMMON STOCK" means the Common Stock of the Company.

                  (d)      "CONSULTANT" means any person, including an advisor,
engaged by the Company or a Parent or Subsidiary to render services to such
entity.

                  (e)      "DIRECTOR" means a member of the Board or a member of
the Board of Directors of any Parent or Subsidiary of the Company.

                  (f)      "DISABILITY" means that Purchaser has been unable to
perform the principal functions of Purchaser's duties due to a physical or
mental impairment, but only if such inability has lasted or is reasonably
expected to last for at least six months. Whether Purchaser has a Disability
will be determined by the Board based on evidence provided by one or more
physicians selected by the Board and reasonably acceptable to Purchaser.

                  (g)      "EMPLOYEE" means any person, including Officers and
Directors, employed by the Company or any Parent or Subsidiary of the Company.
An Employee shall not cease to be such in the case of (i) any leave of absence
approved by the Company or (ii) transfers between locations of the Company or
between the Company, its Parent, any Subsidiary, or any successor. Neither
service as a Director nor payment of a director's fee by the Company shall be
sufficient to constitute "employment" by the Company.

                  (h)      "PARENT" means a "parent corporation", whether now or
hereafter existing, as defined in Section 424(e) of the Code.

                  (i)      "SUBSIDIARY" means a "subsidiary corporation",
whether now or hereafter existing, as defined in Section 424(f) of the Code.

                  (j)      "UNVESTED SHARES" means those Shares that, as of any
particular date, have not vested in accordance with the vesting schedule set
forth in Section 4 below.

                  (k)      "VESTED SHARES" means those Shares that, as of any
particular date, have vested in accordance with the vesting schedule set forth
in Section 4 below.

                                      -2-
<PAGE>

         4.       VESTING.

                  Subject to any acceleration provisions provided for in the
Company's Change of Control Severance Plan or any other agreements between
Purchaser and the Company, the Shares shall vest and be released from the
Company's Repurchase Option (as hereinafter defined) in accordance with the
following provisions:

                  (a)      Twenty-five percent (25%) of the Shares (rounded down
to the next whole number of shares) shall vest one year after the "Vesting
Commencement Date" (as defined below), and 1/48th of the Shares (rounded down to
the next whole number of shares) shall vest each month thereafter on the date
corresponding to the Vesting Commencement Date, so that all of the Shares shall
be vested on the forty-eighth (48th) month anniversary of the Vesting
Commencement Date, subject to, with respect to each vesting date, Purchaser
continuing to be either an Employee or a Consultant of the Company on such
vesting date.

                  (b)      Vesting under this Section shall cease in the event
that Purchaser ceases to be either an Employee or a Consultant; provided,
however, that if Purchaser is terminated by the Company other than for Cause (as
such term is defined in the Company's Amended and Restated 2000 Equity Incentive
Plan) prior to the one-year anniversary of the Vesting Commencement Date, 1/48th
of the Shares (rounded down to the next whole number of shares) shall be deemed
to have vested on the one-month anniversary of the Vesting Commencement Date and
on each monthly anniversary thereafter until the date of such termination. At
such times, the repurchase provisions of Section 5 hereof shall apply to all
Shares that are Unvested Shares as of the date of such termination.

                  (c)      The Vesting Commencement Date shall be August 1,
2003.

         5.       REPURCHASE OPTION.

                  (a)      If Purchaser's status as an Employee or a Consultant
terminates for any or no reason, the Company shall have the right and option
(the "REPURCHASE OPTION") to purchase from Purchaser all of Purchaser's Shares
which are Unvested Shares as of the date of such termination, at the price paid
by Purchaser for such Shares (the "REPURCHASE PRICE").

                  (b)      The Repurchase Option shall be exercised by the
Company by delivering written notice to the Purchaser or the Purchaser's
executor (with a copy to the Escrow Agent (as defined below)) AND, at the
Company's option, (i) by delivering to the Purchaser or the Purchaser's executor
a check in the amount of the aggregate Repurchase Price, or (ii) by canceling an
amount of the Purchaser's indebtedness to the Company equal to the aggregate
Repurchase Price, or (iii) by a combination of (i) and (ii) so that the combined
payment and cancellation of indebtedness equals the aggregate Repurchase Price.
Upon delivery of such notice and the payment of the aggregate Repurchase Price,
the Company shall become the legal and beneficial owner of the Shares being
repurchased and all rights and interests therein or relating thereto, and the
Company shall have the right to retain and transfer to its own name the number
of Shares being repurchased by the Company.

                                      -3-
<PAGE>

                  (c)      If the Company does not elect to exercise the
Repurchase Option conferred above by giving the requisite notice within ninety
(90) days following the termination, the Repurchase Option shall terminate.

         6.       TRANSFER OF SHARES; ESCROW.

                  (a)      Purchaser hereby authorizes and directs the Escrow
Agent (as defined below) to transfer any Unvested Shares as to which the
Repurchase Option has been exercised from Purchaser to the Company.

                  (b)      To ensure the availability for delivery of
Purchaser's Unvested Shares upon repurchase by the Company pursuant to the
Repurchase Option under Section 5 above, Purchaser hereby appoints the Corporate
Secretary of the Company, or any other person designated by the Company, as
escrow agent (the "ESCROW AGENT") and as Purchaser's attorney-in-fact to sell,
assign and transfer unto the Company such Unvested Shares, if any, as may be
repurchased by the Company pursuant to the Repurchase Option and shall, upon
execution of this Agreement, deliver and deposit with the Escrow Agent the share
certificates representing the Shares, together with two stock assignments duly
endorsed in blank and in the form attached hereto as Exhibit A-1. The share
certificates representing the Shares and stock assignment shall be held by the
Escrow Agent in escrow pursuant to Joint Escrow Instructions in the form
attached hereto as Exhibit A-2, until (i) the Company exercises its Repurchase
Option as provided in Section 5 above or (ii) such time as this Agreement no
longer is in effect. Notwithstanding any of the foregoing, however, the Escrow
Agent shall nevertheless retain such certificate or certificates as Escrow Agent
if so required pursuant to other restrictions imposed pursuant to this
Agreement.

                  (c)      The Escrow Agent shall not be liable for any act it
may do or omit to do with respect to holding the Shares in escrow and while
acting in good faith and in the exercise of its judgment.

                  (d)      Transfer or sale of the Shares is subject to
restrictions on transfer imposed by any applicable state and federal securities
laws. Any transferee shall hold such Shares subject to all the provisions hereof
and shall acknowledge the same by signing a copy of this Agreement.

                  (e)      No Shares may be sold, pledged, hypothecated or
otherwise transferred by Purchaser until such Shares have become Vested Shares
and are no longer subject to any security agreement for the benefit of the
Company.

         7.       OWNERSHIP, VOTING RIGHTS, DUTIES. This Agreement shall not
affect in any way the ownership, voting rights or other rights or duties of
Purchaser, except as specifically provided herein. Purchaser shall enjoy rights
as a stockholder until such time as Purchaser disposes of the Shares or the
Company and/or its assignee(s) exercises the Repurchase Option hereunder. Upon
any such exercise, Purchaser shall have no further rights as a holder of the
Shares so purchased except the right to receive payment for the Shares so
purchased in accordance with the provisions of this Agreement, and Purchaser or
the Escrow Agent, as the case may be, shall forthwith cause the certificate(s)
evidencing the Shares so purchased to be surrendered to the Company for transfer
or cancellation.

                                      -4-
<PAGE>

         8.       RESTRICTIVE LEGENDS; STOP-TRANSFER ORDERS.

                  (a)      LEGENDS. Purchaser understands and agrees that the
Company shall cause the legends set forth below or legends substantially
equivalent thereto, to be placed upon any certificate(s) evidencing ownership of
the Shares together with any other legends that may be required by state or
federal securities laws:

                  THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
                  CERTAIN RESTRICTIONS ON TRANSFER AND RIGHTS OF REPURCHASE FOR
                  THE BENEFIT OF CAPSTONE TURBINE CORPORATION OR ITS ASSIGNEE(S)
                  AS SET FORTH IN A RESTRICTED STOCK PURCHASE AGREEMENT BETWEEN
                  CAPSTONE TURBINE CORPORATION AND THE ORIGINAL HOLDER OF THESE
                  SHARES, COPIES OF WHICH MAY BE OBTAINED AT THE PRINCIPAL
                  OFFICE OF CAPSTONE TURBINE CORPORATION. SUCH TRANSFER
                  RESTRICTIONS AND RIGHTS OF REPURCHASE ARE BINDING ON
                  TRANSFEREES OF THESE SHARES.

                  (b)      STOP-TRANSFER NOTICES. Purchaser agrees that, in
order to ensure compliance with the restrictions referred to herein, the Company
may issue appropriate "stop transfer" instructions to its transfer agent, if
any, and that, if the Company transfers its own securities, it may make
appropriate notations to the same effect in its own records.

         9.       SECTION 83(b) ELECTIONS. Purchaser understands that Section 83
of the Code, taxes as ordinary income the difference between the amount paid for
the Shares and the fair market value of the Shares as of the date any
restrictions on the Shares lapse. In this context, "restriction" means the right
of the Company to buy back the Shares pursuant to the Repurchase Option. Because
the Company has registered equity securities under the Securities Exchange Act
of 1934 (the "EXCHANGE ACT"), "restriction" with respect to officers, directors,
and ten percent (10%) stockholders also includes the six-month period after the
purchase of the Shares during which sales of certain securities by such
officers, directors, and ten percent (10%) stockholders would give rise to
liability under Section 16(b) of the Exchange Act. Purchaser understands that he
may elect to be taxed at the time the Shares are purchased rather than when any
restrictions applicable to the Shares lapse, by filing an election under Section
83(b) of the Code with the Internal Revenue Service within thirty (30) days from
the date of purchase. Even if the fair market value of the Shares equals the
amount paid for the Shares, the election may be made to avoid adverse tax
consequences in the future. Purchaser understands that failure to make this
filing in a timely manner shall result in the recognition of ordinary income by
Purchaser, as any restrictions applicable to the Shares lapse, on any difference
between the purchase price and the fair market value of the Shares at the time
such restrictions lapse. A form of Election under Section 83(b) is attached to
the Agreement as Exhibit A -3 for reference.

                  PURCHASER ACKNOWLEDGES THAT IT IS PURCHASER'S SOLE
RESPONSIBILITY AND NOT THE COMPANY'S TO FILE TIMELY THE ELECTION UNDER SECTION
83(b) OF THE CODE, EVEN IF PURCHASER REQUESTS THE COMPANY OR ITS REPRESENTATIVE
TO MAKE THIS FILING ON PURCHASER'S BEHALF.

                                      -5-
<PAGE>

         10.      ADDITIONAL ACTIONS. The parties shall execute such further
instruments and take such further action as may reasonably be necessary to carry
out the intent of this Agreement.

         11.      ASSIGNMENT. The Company may assign its rights and delegate its
duties under this Agreement. This Agreement shall inure to the benefit of the
successors and assigns of the Company and, subject to the restrictions on
transfer herein set forth, be binding upon Purchaser, Purchaser's heirs,
executors, administrators, successors and assigns.

         12.      ENTIRE AGREEMENT; AMENDMENT. This Agreement and the Joint
Escrow Instructions executed in connection herewith constitute the full and
entire understanding and agreement between the parties with regard to the
subjects hereof and thereof, and no party shall be liable or bound to any other
party in any manner by any warranties, representations or covenants except as
specifically set forth herein. Except as expressly provided herein, neither this
Agreement nor any term hereof may be amended, waived, discharged or terminated
other than by a written instrument signed by the party against whom enforcement
of any such amendment, waiver, discharge or termination is sought.

         13.      GOVERNING LAW. This Agreement shall be governed by and
construed and enforced in accordance with the laws of the State of California as
they apply to contracts entered into and wholly to be performed within such
state.

                  Purchaser represents that Purchaser has read this Agreement
and is familiar with its terms and provisions. Purchaser hereby agrees to accept
as binding, conclusive and final all decisions or interpretations of the Board
upon any questions arising under this Agreement.

         14.      NO GUARANTEE OF CONTINUED SERVICE. PURCHASER ACKNOWLEDGES AND
AGREES THAT THIS AGREEMENT AND THE TRANSACTIONS CONTEMPLATED HEREUNDER DO NOT
CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS AN EMPLOYEE
OR A CONSULTANT OF THE COMPANY FOR ANY PERIOD OR AT ALL. NOTHING IN THIS
AGREEMENT SHALL AFFECT IN ANY MANNER WHATSOEVER OR INTERFERE WITH THE RIGHT OR
POWER OF THE COMPANY, OR A PARENT OR SUBSIDIARY OF THE COMPANY, TO TERMINATE
PURCHASER'S RELATIONSHIP WITH THE COMPANY AT ANY TIME, FOR ANY OR NO REASON,
WITH OR WITHOUT CAUSE.

         15.      ADVICE OF COUNSEL. Purchaser has reviewed this Agreement in
its entirety, has had an opportunity to obtain the advice of independent counsel
prior to executing this Agreement and fully understands all provisions hereof.

         16.      AUTHORIZATION OF TRANSFER. Purchaser hereby authorizes and
directs the Secretary or transfer agent of the Company to transfer the Stock as
to which the Repurchase Option has been exercised from Purchaser to the Company
or the Company's assignees.

         17.      WAIVER. Either party's failure to enforce any provision or
provisions of this Agreement shall not in any way be construed as a waiver of
any such provision or provisions, nor prevent that party thereafter from
enforcing each and every other provision of this Agreement. The

                                      -6-
<PAGE>

rights granted both parties herein are cumulative and shall not constitute a
waiver of either party's right to assert all other legal remedies available to
it under the circumstances.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                      -7-
<PAGE>

         IN WITNESS WHEREOF, this Agreement is deemed made as of the date first
set forth above.

                                         CAPSTONE TURBINE CORPORATION

                                         By:
                                             -----------------------------------

                                         Name: Karen Clark

                                         Title: Senior Vice President, Chief
                                         Financial Officer

                                         PURCHASER

                                         ---------------------------------------
                                         John Tucker

                                         ADDRESS:

                                         450 Ironwood Drive
                                         Canonsburg, PA 15317

            [SIGNATURE PAGE FOR RESTRICTED STOCK PURCHASE AGREEMENT]

                                      -8-
<PAGE>

                                  EXHIBIT A-1

                      ASSIGNMENT SEPARATE FROM CERTIFICATE

         FOR VALUE RECEIVED, John Tucker hereby sells, assigns and transfers
unto Capstone Turbine Corporation, an aggregate of ___________ shares of the
Common Stock of Capstone Turbine Corporation standing in the undersigned's name
on the books of said corporation represented by Certificate No. _____, and does
hereby irrevocably constitute and appoint _________________________________ to
transfer the said stock on the books of the within named corporation with full
power of substitution in the premises.

         This Stock Assignment may be used only in accordance with the
Restricted Stock Purchase Agreement between Capstone Turbine Corporation and the
undersigned dated August ___, 2003 (the "AGREEMENT").

Dated:

                                                        ________________________
                                                        John Tucker

INSTRUCTIONS: Please do not fill in the blanks other than the signature line.
The purpose of this assignment is to enable the Company to exercise its
"Repurchase Option," as set forth in the Agreement, without requiring additional
signatures on the part of the Purchaser.

<PAGE>

                                   EXHIBIT A-2

                            JOINT ESCROW INSTRUCTIONS

                                                           August _______, 2003

Capstone Turbine Corporation
Attn: Corporate Secretary
21211 Nordhoff Street
Chatsworth, CA 91311

Dear Corporate Secretary:

         As Escrow Agent for both Capstone Turbine Corporation, a Delaware
corporation (the "COMPANY"), and the undersigned purchaser of stock of the
Company ("PURCHASER"), you are hereby authorized and directed to hold the
documents delivered to you pursuant to the terms of that certain Restricted
Stock Purchase Agreement (the "AGREEMENT"), dated as of August ____, 2003,
between the Company and the undersigned, in accordance with the following
instructions:

         1.       In the event that the Company and/or any assignee of the
Company (referred to collectively for convenience herein as the "COMPANY")
exercises the Company's "Repurchase Option" set forth in the Agreement, the
Company shall give to Purchaser and you a written notice specifying the number
of shares of stock to be purchased, the purchase price, and the time for a
closing hereunder at the principal office of the Company. Purchaser and the
Company hereby irrevocably authorize and direct you to close the transaction
contemplated by such notice in accordance with the terms of said notice.

         2.       At the closing, you are directed (a) to date the stock
assignments necessary for the transfer in question, (b) to fill in the number of
shares being transferred, and (c) to deliver same, together with the certificate
evidencing the shares of stock to be transferred, to the Company or its
assignee, against the simultaneous delivery to you of the purchase price (as
permitted in the Agreement) for the number of shares of stock being purchased
pursuant to the exercise of the Company's Repurchase Option.

         3.       Purchaser irrevocably authorizes the Company to deposit with
you any certificates evidencing shares of stock to be held by you hereunder and
any additions and substitutions to said shares as defined in the Agreement.
Purchaser does hereby irrevocably constitute and appoint you as Purchaser's
attorney-in-fact and agent for the term of this escrow to execute with respect
to such securities all documents necessary or appropriate to make such
securities negotiable and to complete any transaction herein contemplated,
including but not limited to the filing with any applicable state blue sky
authority of any required applications for consent to, or notice of transfer of,
the securities. Subject to the provisions of this paragraph 3, Purchaser shall
exercise all rights and privileges of a stockholder of the Company while the
stock is held by you.

         4.       Upon written request of Purchaser, but no more than once per
calendar year, unless the Company's repurchase option has been exercised, you
shall deliver to Purchaser a certificate or certificates representing so many
shares of stock as are not then subject to the Company's

<PAGE>

Repurchase Option. Within 120 days after cessation of Purchaser's continuous
employment by or services to the Company, or any parent or subsidiary of the
Company, you shall deliver to Purchaser a certificate or certificates
representing the aggregate number of shares held or issued pursuant to the
Agreement and not purchased by the Company or its assignees pursuant to exercise
of the Company's Repurchase Option.

         5.       If at the time of termination of this escrow you should have
in your possession any documents, securities, or other property belonging to
Purchaser, you shall deliver all of the same to Purchaser and shall be
discharged of all further obligations hereunder.

         6.       Your duties hereunder may be altered, amended, modified or
revoked only by a writing signed by all of the parties hereto.

         7.       You shall be obligated only for the performance of such duties
as are specifically set forth herein and may rely and shall be protected in
relying or refraining from acting on any instrument reasonably believed by you
to be genuine and to have been signed or presented by the proper party or
parties. You shall not be personally liable for any act you may do or omit to do
hereunder as Escrow Agent or as attorney-in-fact for Purchaser while acting in
good faith, and any act done or omitted by you pursuant to the advice of your
own attorneys shall be conclusive evidence of such good faith.

         8.       You are hereby expressly authorized to disregard any and all
warnings given by any of the parties hereto or by any other person or
corporation, excepting only orders or process of courts of law and are hereby
expressly authorized to comply with and obey orders, judgments or decrees of any
court. In case you obey or comply with any such order, judgment or decree, you
shall not be liable to any of the parties hereto or to any other person, firm or
corporation by reason of such compliance, notwithstanding any such order,
judgment or decree being subsequently reversed, modified, annulled, set aside,
vacated or found to have been entered without jurisdiction.

         9.       You shall not be liable in any respect on account of the
identity, authorities or rights of the parties executing or delivering or
purporting to execute or deliver the Agreement or any documents or papers
deposited or called for hereunder.

         10.      You shall not be liable for the outlawing of any rights under
the Statute of Limitations with respect to these Joint Escrow Instructions or
any documents deposited with you.

         11.      You shall be entitled to employ such legal counsel and other
experts as you may deem necessary properly to advise you in connection with your
obligations hereunder, may rely upon the advice of such counsel, and may pay
such counsel reasonable compensation therefor.

         12.      Your responsibilities as Escrow Agent hereunder shall
terminate if you shall cease to be an officer or agent of the Company or if you
shall resign by written notice to each party. In the event of any such
termination, the Company shall appoint a successor Escrow Agent.

         13.      If you reasonably require other or further instruments in
connection with these Joint Escrow Instructions or obligations in respect
hereto, the necessary parties hereto shall join in furnishing such instruments.

                                      -2-
<PAGE>

         14.      It is understood and agreed that should any dispute arise with
respect to the delivery and/or ownership or right of possession of the
securities held by you hereunder, you are authorized and directed to retain in
your possession without liability to anyone all or any part of said securities
until such disputes shall have been settled either by mutual written agreement
of the parties concerned or by a final order, decree or judgment of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

         15.      All notices and other communications required or permitted
hereunder shall be in writing, shall be effective when given, and shall in any
event be deemed to be given (a) five (5) days after deposit with the U.S. Postal
Service, if delivered by first class mail, postage prepaid, (b) upon delivery,
if delivered by hand, or (c) one business day after the business day of deposit
with Federal Express or similar overnight courier, freight prepaid, and shall be
addressed to each of the other parties thereunto entitled at the following
addresses or at such other addresses as a party may designate by ten days'
advance written notice to each of the other parties hereto.

                  COMPANY:          Capstone Turbine Corporation
                                    21211 Nordhoff Street
                                    Chatsworth, CA 91311
                                    Attn: Chairman of the Board of Directors

                                    with a copy to:

                                    Capstone Turbine Corporation
                                    21211 Nordhoff Street
                                    Chatsworth, CA 91311
                                    Attn: Chief Financial Officer

                  PURCHASER:        John Tucker
                                    450 Ironwood Drive
                                    Canonsburg, PA 15317

                  ESCROW AGENT:     Capstone Turbine Corporation
                                    21211 Nordhoff Street
                                    Chatsworth, CA 91311
                                    Attn: Corporate Secretary

         16.      By signing these Joint Escrow Instructions, you become a party
hereto only for the purpose of said Joint Escrow Instructions; you do not become
a party to the Agreement.

         17.      This instrument shall be binding upon and inure to the benefit
of the parties hereto, and their respective successors and permitted assigns.

         18.      These Joint Escrow Instructions shall be governed by, and
construed and enforced in accordance with, the laws of the State of California
as they apply to contracts entered into and wholly to be performed within such
state.

                                      -3-
<PAGE>

                                          Very truly yours,

                                          CAPSTONE TURBINE CORPORATION

                                          PURCHASER:

                                          ______________________________________
                                          John Tucker

                                          ESCROW AGENT:

                                          ______________________________________
                                          Corporate Secretary

                                      -4-
<PAGE>

                                   EXHIBIT A-3

                          ELECTION UNDER SECTION 83(b)
                      OF THE INTERNAL REVENUE CODE OF 1986

         The undersigned taxpayer hereby elects, pursuant to the
above-referenced Federal Tax Code, to include in taxpayer's gross income for the
current taxable year, the amount of any compensation taxable to taxpayer in
connection with his receipt of the property described below:

1.       The name, address, taxpayer identification number and taxable year of
         the undersigned are as follows:

         NAME :            TAXPAYER:                          SPOUSE:

         ADDRESS:

         IDENTIFICATION NO.: TAXPAYER:                        SPOUSE:

         TAXABLE YEAR: Calendar Year _____

2.       The property with respect to which the election is made is described as
         follows: _____ shares (the "SHARES") of the Common Stock of Capstone
         Turbine Corporation, a Delaware corporation (the "COMPANY").

3.       The date on which the property was transferred is:_____________, _____.

4.       The property is subject to the following restrictions:

         The Shares may be repurchased by the Company, or its assignee, on
         certain events. This right lapses with regard to a portion of the
         Shares based on the continued performance of services by the taxpayer
         over time.

5.       The fair market value at the time of transfer, determined without
         regard to any restriction other than a restriction which by its terms
         will never lapse, of such property is: $_____.

6.       The amount (if any) paid for such property is: $________.

The undersigned has submitted a copy of this statement to the person for whom
the services were performed in connection with the undersigned's receipt of the
above-described property. The transferee of such property is the person
performing the services in connection with the transfer of said property.

The undersigned understands that the foregoing election may not be revoked
except with the consent of the Commissioner.

Dated:________________________, _____           ________________________________
                                                Taxpayer

The undersigned spouse of taxpayer joins in this election.

Dated:________________________, _____           ________________________________
                                                Spouse of Taxpayer

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