Document:

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                                                                     EXHIBIT 4.1

                              EXTENSIBILITY, INC.

                                2000 STOCK PLAN

     1.   PURPOSE.  The purpose of this Plan is to advance the interests of
Extensibility, Inc. (the "Company") by providing an opportunity to its selected
key employees (as defined in Section 2(b)) and consultants (as defined in
Section 2(a)) to purchase shares (the "Shares") of the Common Stock, par value
$.01 per share (the "Common Stock"), of the Company. By encouraging stock
ownership, the Company seeks to attract, retain and motivate key employees and
consultants. It is intended that this purpose will be effected by the granting
of (i) incentive stock options ("Incentive Options") as described in Section 422
of the Internal Revenue Code of 1986, as amended (the "Code"); (ii) nonqualified
stock options ("Nonqualified Options," and, together with the incentive options,
the "Options") as provided herein; and (iii) rights to purchase shares of Common
Stock ("Restricted Stock") of the Company pursuant to restricted stock
agreements and subscription agreements as provided herein ("Purchase Rights" and
collectively with the options, the "Stock Incentives").

     2.   DEFINITIONS.

          (a)  The term "consultants" means those persons, other than employees
of the Company, who provide services to the Company, including nonemployee
directors of the Company, and who are determined by the Board of Directors to be
eligible for Stock Incentives under this Plan.

          (b)  The term "key employees" means those executive, administrative,
operational, engineering or managerial employees who are determined by the Board
of Directors to be eligible for Stock Incentives under this Plan.

          (c)  The term "optionee" means an individual to whom an option is
granted under this Plan.

          (d)  The term "grantee" means an individual to whom a purchase right
is granted under this Plan.

     3.   EFFECTIVE DATE.  This Plan became effective on January 31, 2000, the
date it was adopted by the Board of Directors of the Company.

     4.   STOCK SUBJECT TO THE PLAN.  The Shares that may be purchased (through
the exercise of options or the purchase of Restricted Stock) under this Plan
shall not exceed in the aggregate 1,187,500 Shares. If any Stock Incentives
granted under the Plan shall terminate, expire or be cancelled as to any Shares,
new Stock Incentives may thereafter be granted covering such Shares. In
addition, any Shares purchased under this Plan subsequently repurchased by the
Company pursuant to the terms hereof may again be granted under the Plan. The
Shares issued upon exercise of Stock Incentives under this Plan may, in whole or
in part, be either authorized but unissued Shares or issued Shares reacquired by
the Company. Notwithstanding any other provisions of this Plan, the aggregate
number of Shares subject to outstanding options granted under the Plan,
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plus the aggregate number of Shares issued upon the exercise of all options
granted under the Plan, shall never be permitted to exceed the number of Shares
specified in the first sentence of this Section 4.

     5.   ADMINISTRATION.  The Plan shall be administered by the Board of
Directors of the Company (the "Board"). The Board may delegate nondiscretionary
administrative duties to such employees of the Company as it deems proper.
Subject to the provisions of the Plan, the Board shall have the sole authority,
in its discretion:

          (a)  to determine to which of the eligible individuals, and the time
or times at which, options to purchase Common Stock of the Company shall be
granted;

          (b)  to determine the number of shares of Common Stock to be subject
to options granted to each eligible individual;

          (c)  to determine the price to be paid for the shares of Common Stock
upon the exercise of each option;

          (d)  to determine the term and the exercise schedule of each option;

          (e)  to determine the terms and conditions of each stock option
agreement (which need not be identical) entered into between the Company and any
eligible individual to whom the Board has granted an option;

          (f)  to interpret the Plan; and

          (g)  to make all determinations deemed necessary or advisable for the
administration of the Plan.

     No member of the Board shall be liable for any action or determination made
with respect to the Plan.

     6.   ELIGIBLE EMPLOYEES AND CONSULTANTS.  Incentive Options may be granted
to such key employees of the Company, including members of the Board of
Directors who are also employees of the Company, as are selected by the Board.
Nonqualified Options and Purchase Rights may be granted to such key employees
and consultants of the Company, including members of the Board of Directors, as
are selected by the Board of Directors. The term "employee" includes an officer
or director who is an employee of the Company or a parent or subsidiary of it,
as well as a nonofficer, nondirector employee of the Company or a parent or
subsidiary of it.

     7.   DURATION OF THE PLAN.  This Plan shall terminate ten (10) years from
the effective date of this Plan, unless terminated earlier pursuant to Section
17 hereof, and no Stock Incentives may be granted after such termination.

                                      -2-
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     8.   RESTRICTIONS ON INCENTIVE OPTIONS.  Incentive Options (but not
Nonqualified Options) granted under this Plan shall be subject to the following
restrictions:

          (a)  Limitation on Number of Shares.  The aggregate fair market value,
determined as of the date the Incentive Option is granted, of the Shares with
respect to which Incentive Options are exercisable for the first time by an
employee during any calendar year shall not exceed $100,000. If an employee is
eligible to participate in any other incentive stock option plans of the Company
which are also intended to comply with the provisions of Section 422 of the
Code, the applicable annual limitation shall apply to the aggregate number of
Shares for which Incentive Options may be granted under all such plans. An
Incentive Option may be granted which exceeds the $100,000 limitation, as long
as under then applicable law the portion of such Option which is exercisable for
shares in excess of the $100,000 limitation shall be treated as a nonqualified
option. No Incentive Options may be exercised until and unless the Plan is
approved by the shareholders within one year of the date hereof, such approval
to be expressed in any legal way under Delaware law.

          (b)  10% Stockholder.  If any employee to whom an Incentive Option is
granted pursuant to the provisions of the Plan is on the date of grant the owner
of stock (as determined under Section 424(d) of the Code) possessing more than
10% of the total combined voting power of all classes of stock of the Company
(or of any parent or subsidiary of the Company), then the following special
provisions shall be applicable to the Incentive Option granted to such
individual:

               (i)  The option price per Share subject to such Incentive Option
                    shall not be less than 110% of the fair market value of one
                    Share on the date of grant; and

               (ii) The Incentive Option shall not have a term in excess of five
                    (5) years from the date of grant.

                    In determining stock ownership, an Optionee shall be
                    considered as owning the voting capital stock owned,
                    directly or indirectly, by or for his brothers and sisters,
                    spouse, ancestors, and lineal descendants. Voting capital
                    stock owned, directly or indirectly, by or for a
                    corporation, partnership, estate or trust shall be
                    considered as being owned proportionately by or for its
                    shareholders, partners, or beneficiaries, as applicable.
                    Common Stock with respect to which any such Optionee holds
                    an option shall not be counted. Additionally, outstanding
                    capital stock shall include all capital stock actually
                    issued and outstanding immediately after the grant of the
                    option to the optionee. Outstanding capital stock shall not
                    include capital stock authorized for issue under outstanding
                    options held by the Optionee or by any other person.

     9.   TERMS AND CONDITIONS OF OPTIONS.  Incentive and Nonqualified Options
granted under this Plan shall be evidenced by stock option agreements in such
form and not

                                      -3-
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inconsistent with the Plan as the Board shall approve from time to time, which
agreements shall evidence the following terms and conditions:

          (a)  Price.

               (i)  Incentive Options.  Subject to the condition of subparagraph
(b)(i) of Section 8, if applicable, with respect to each Incentive Option, the
purchase price per Share payable upon the exercise of each Incentive Option
granted hereunder shall be determined by the Board and shall be not less than
100% of the fair market value of one Share on the day the option is granted.

               (ii) Nonqualified Options.  With respect to each Nonqualified
Option, the purchase price per Share payable upon the exercise of each
Nonqualified Option granted hereunder shall be determined by the Board at the
time the Nonqualified Option is granted.

          (b)  Number of Shares.  Each option agreement shall specify the number
of Shares to which it pertains.

          (c)  Exercise.  Subject to the conditions of subparagraphs (a) and
(b)(ii) of Paragraph 8, if applicable, each option shall be exercisable for the
full amount or for any part thereof and at such intervals or in such
installments as the Board may determine at the time it grants such option;
provided, however, that no option shall be exercisable with respect to any
Shares later than ten (10) years after the date of the grant of such option.

          (d)  Notice of Exercise and Payment. An option shall be exercisable
only by delivery of a written notice to the Board, any member of the Board, the
Company's Treasurer, or any other officer of the Company designated by the Board
to accept such notices on its behalf, specifying the number of Shares for which
it is exercised. If such Shares are not at the time effectively registered under
the Securities Act of 1933, as amended, the Optionee shall include with such
notice a letter, in form and substance satisfactory to the Company, confirming
that such Shares are being purchased for the optionee's own account for
investment and not with a view to the resale or distribution thereof. Payment
shall be made in full at the time of delivery to the optionee of a certificate
or certificates covering the number of Shares for which the option was
exercised. Payment shall be made (i) by cash, check, bank wire, or other form of
payment, (ii) if permitted by the Board, by delivery and assignment to the
Company of shares of the Company's stock having a fair market value (as
determined by the Board) equal to the exercise price, (iii) if permitted by the
Board, by a promissory note, (iv) by a combination of (i), (ii), and (iii) or
(v) by a combination of (i), (ii), (iii), and (iv) by a cashless exercise of
vested options, i.e., surrender of vested options to purchase the number of
shares resulting from the formula X=<Y(A-B)> divided by A, where X is the number
of fully paid shares to be issued by the Company in consideration for the vested
options surrendered, Y is the number of vested options being surrendered, A is
the fair market value (as determined by the Board) of the Common Stock at the
time of exercise, and B is the exercise price of the option being exercised. The
value of the shares of the Company's stock for such purpose shall be its fair
market value as of the date the option is exercised, as determined in accordance
with procedures to be established by the Board.

                                      -4-
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          (e)  Withholding Taxes; Delivery of Shares.  The Company's obligation
to deliver Shares upon exercise of a Nonqualified Option, in whole or in part,
shall be subject to the Optionee's satisfaction of all applicable federal,
state, and local income and employment tax withholding obligations. The Optionee
may satisfy the obligation, in whole or in part, by electing to have the Company
withhold Shares having a value equal to the amount required to be withheld. The
value of Shares to be withheld shall be based on the fair market value of the
Shares on the date the amount of tax to be withheld is to be determined. If
Common Stock acquired by exercise of an incentive stock option granted pursuant
to this Plan is disposed of within two (2) years from the date of grant of the
option or within one (1) year after the transfer of the Common Stock to the
optionee, the holder of the Common Stock immediately prior to the disposition
shall promptly notify the Company in writing of the date and terms of the
disposition and shall provide such other information regarding the disposition
as the Company may reasonably require.

          (f)  Nontransferability.  No option shall be transferable by the
Optionee otherwise than by will or the laws of descent or distribution, and each
otherwise provided for in subparagraph (g) below).

          (g)  Termination of Options.  Each option shall terminate and may no
longer be exercised if the Optionee ceases for any reason to be an employee of,
or consultant to, the Company, except that:

               (i)    if the Optionee's performance of services shall have
                      terminated for any reason other than cause (which shall
                      mean Optionee's willful misconduct or gross negligence, as
                      reasonably determined by the Board, in its sole
                      discretion) disability (as defined below) or death, he may
                      at any time within a period of three (3) months after such
                      termination of the performance of services exercise his
                      option to the extent that the option was exercisable by
                      him on the date of termination of his performance of
                      services;

               (ii)   if the Optionee's performance of services shall have been
                      terminated because of disability within the meaning of
                      Section 22(e)(3) of the Internal Revenue Code, the
                      Optionee may, at any time within a period of one (1) year
                      after the termination of performance of services, exercise
                      his option to the extent that the option was exercisable
                      by him on the date of termination of his employment or
                      performance of services; and

               (iii)  if the Optionee dies at a time when the option was
                      exercisable by him, then his estate, personal
                      representative or beneficiary to whom it has been
                      transferred may exercise the option to the extent the
                      Optionee might have exercised it at the time of his death,
                      at any time within a period of one(1) year following his
                      death if the Optionee's performance of services shall have
                      been terminated by his death;

                                      -5-
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                    provided, however, that no option may be exercised to any
                    extent by anyone after the date of expiration of the option.

          (h)  Rights as Stockholder.  The Optionee shall have no rights as a
stockholder with respect to any Shares covered by his option until the date of
issuance of a stock certificate to him for such Shares.

          (i)  Repurchase of Shares by the Company. Any Shares purchased by an
Optionee upon exercise of an option may in the discretion of the Board be
subject to repurchase by the Company if and to the extent specifically set forth
in the agreement pursuant to which the Shares were purchased.

     10.  TERMS AND CONDITIONS OF PURCHASE RIGHTS.  Purchase Rights granted
under this Plan shall be evidenced by restricted stock agreements and
subscription agreements in such form and not inconsistent with the Plan as the
Board shall approve from time to time, which agreements shall include the
following terms and conditions:

          (a)  Price.  The purchase price of each Share purchased by key
employees or consultants pursuant to a Purchase Right hereunder shall be the
price determined by the Board at the time such Purchase Right is granted.

          (b)  Number of Shares.  Each restricted stock agreement and
subscription agreement shall specify the number of Shares to which it pertains.

          (c)  Investment Intent and Payment.  If the Shares purchased are not
at the time effectively registered under the Securities Act of 1933, as amended,
the restricted stock agreement and subscription agreement shall provide that the
grantee is purchasing such Shares for the grantee's own account for investment
and not with a view to the resale or distribution thereof. Payment shall be made
in full at the time of delivery to the Company by the grantee of an executed
restricted stock agreement and subscription agreement covering the number of
Shares for which the Purchase Right was granted. An officer or an agent of the
Company shall be entitled to retain in escrow for the benefit of the grantee
stock certificates representing Shares which are subject to a repurchase option
of the Company, as described in subparagraph (f) below. Payment for Shares shall
be made (i) by cash or check, (ii) if permitted by the Board, by delivery and
assignment to the Company of shares of the Company's stock having a fair market
value (as determined by the Board) equal to the purchase price, (iii) if
permitted by the Board, by a promissory note, or (iv) by a combination of (i),
(ii), and (iii). The value of the shares of the Company's stock for such purpose
shall be its fair market value as of the date of the restricted stock agreement,
as determined in accordance with procedures to be established by the Board.

          (d)  Withholding Taxes.  The Company's obligation to deliver the
Shares to the grantee shall be subject to the grantee's satisfaction of all
applicable federal, state, and local income and employment tax withholding
obligations. The grantee may satisfy such withholding obligations, in whole or
in part, by electing to have the Company withhold Shares having a value equal to
the amount required to be withheld. The value of the Shares to be withheld shall
be based on the fair market value of such Shares as of the date the amount of
tax is to be determined.

                                      -6-
<PAGE>

          (e)  Nontransferability.  Any Shares purchased by a grantee pursuant
to a purchase right hereunder may, in the discretion of the Board, be subject to
transfer restrictions if and to the extent specifically set forth in the
restricted stock agreement governing such purchase.

          (f)  Repurchase of Shares by the Company.  Any Shares purchased by a
grantee pursuant to a Purchase Right hereunder may, in the discretion of the
Board, be subject to repurchase by the Company if and to the extent set forth in
the restricted stock agreement governing such purchase.

          (g)  Rights as Stockholder.  Except for the limitations on
transferability and the Company's repurchase rights set forth above, the grantee
of a Purchase Right shall, upon purchase of Shares, possess all rights as a
holder of Common Stock of the Company.

     11.  STOCK DIVIDENDS; STOCK SPLITS; STOCK COMBINATIONS; RECAPITALIZATIONS.
Appropriate adjustment shall be made in the maximum number of Shares of Common
Stock subject to the Plan and in the number, kind and price of Shares covered by
any Stock Incentive granted hereunder to give effect to any stock dividends or
other distributions, stock splits, stock combinations, recapitalizations and
other similar changes in the capital structure of the Company after the
effective date of the Plan.

     12.  MERGER; SALE OF ASSETS; DISSOLUTION.  In the event of a change of the
Common Stock resulting from a merger or similar reorganization as to which the
Company is the surviving corporation, the number and kind of shares which
thereafter may be subject to Stock Incentives granted under this Plan and the
number, kind and price of Shares then subject to Stock Incentives shall be
appropriately adjusted in such manner as the Board may deem equitable to prevent
substantial dilution or enlargement of the rights available or granted
hereunder. Except as set forth in any stock option agreement or as otherwise
determined by the Board of Directors of the Company, a merger or a similar
reorganization that the Company does not survive, or a sale of all or
substantially all of the assets of the Company, shall cause every Incentive
Option and Nonqualified Option outstanding hereunder to terminate, to the extent
not then exercised, unless any surviving entity agrees to assume the obligations
hereunder.

     13.  NO RIGHTS.  Except as hereinabove expressly provided in Sections 11
and 12, no optionee shall have any rights by reason of any subdivision or
consolidation of shares of the capital stock of any class or the payment of any
stock dividend or any other increase or decrease in the number of shares of any
class or by reason of any dissolution, liquidation, merger or consolidation or
spin-off of assets or stock of another corporation, and any issue by the Company
of shares of stock of any class or of securities convertible into shares of
stock of any class shall not affect, and no adjustment by reason thereof shall
be made with respect to, the number or price of shares subject to any option
granted hereunder. The grant of an option pursuant to this Plan shall not affect
in any way the right or power of the Company to make adjustments,
reclassifications, reorganizations or changes of its capital or business
structure or to merge or consolidate or to dissolve, liquidate, sell, or
transfer all or any part of its business or assets.

     14.  COMPLIANCE WITH APPLICABLE LAWS.  Notwithstanding any other provision
of the Plan, the Company shall have no liability to issue any shares under the
Plan unless such

                                      -7-
<PAGE>

issuance would comply with all applicable laws and the applicable requirements
of any securities exchange or similar entity. Prior to the issuance of any
shares under the Plan, the Company may require a written statement that the
recipient is acquiring the shares for investment and not for the purpose or with
the intention of distributing the shares. If the redistribution of shares is
restricted pursuant to this Section 14, certificates representing such shares
may bear a legend referring to such restrictions.

     15.  DEATH OF A PARTICIPANT.  In the event of the death of an Optionee, any
options which the Optionee was entitled to exercise on the date immediately
preceding his death shall be exercisable by the person or persons to whom those
rights pass by will or by the laws of descent and distribution. Any such
exercise shall be by written notice thereof filed with the Secretary of the
Company at the Company's corporate headquarters prior to the option's expiration
date, and any person exercising such an option shall be treated as an Optionee
for purposes of the provisions of this Plan.

     16.  EMPLOYMENT STATUS.  The Plan does not constitute a contract of
employment, and selection as an Optionee will not give any employee the right to
be retained in the employ of the Company. The grant of an option under the Plan
shall not confer upon the holder thereof any right as a shareholder of the
Company.

     17.  TERMINATION OR AMENDMENT OF PLAN.  The Board of Directors may at any
time terminate this Plan or make such changes in or additions to the Plan as it
deems advisable without further action on the part of the stockholders of the
Company, provided that no such termination or amendment shall adversely affect
or impair any then outstanding Stock Incentive without the consent of the person
holding such Stock Incentive.

     18.  TERMINATION.  The Plan shall terminate automatically on January 31,
2010, and may be terminated at any earlier date by the Board. No option shall be
granted hereunder after termination of the Plan, but such termination shall not
affect the validity of any option then outstanding.

     19.  TIME OF GRANTING OPTIONS.  The date of grant of an option hereunder
shall, for all purposes, be the date on which the Board makes the determination
granting such option.

     20.  RESERVATION OF SHARES.  The Company, during the term of this Plan,
will at all times reserve and keep available such number of shares of its Common
Stock as shall be sufficient to satisfy the requirements of the Plan.

     21.  EFFECTIVE DATE.  This Plan was adopted by the Board of Directors in
accordance with the requirements of the Internal Revenue Code and the Delaware
General Corporation Law of the Company on January 31, 2000, and shall be
effective on said date, provided the Plan is approved by the shareholders within
twelve (12) months of said date. Options may be granted, but may not be
exercised, prior to the date of such shareholder approval.

                                      -8-
<PAGE>

     22.  CORPORATION FINANCIAL INFORMATION.  The Company shall provide all
optionees on an annual basis with a balance sheet and income statement for the
then ending fiscal year.

                                      -9-<PAGE>

       [Number]                                           [Shares]

                               [LOGO OF KYPHON]

             INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

                                                       CUSIP 501577 10 0
                                             SEE REVERSE FOR CERTAIN DEFINITIONS

THIS CERTIFIES THAT

Is the record holder of

    FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $.001 PAR VALUE OF
          ------------------------             ----------------------
    ------------------------------ KYPHON INC. ----------------------------
            ----------------------             --------------------

transferable on the books of the Corporation by the holder hereof in person or
by duly authorized Attorney upon surrender of this certificate properly
endorsed. This certificate is not valid until countersigned by the Transfer
Agent and Registrar.

WITNESS the facsimile seal of the Corporation and the facsimile signatures of
its duly authorized officers.

Dated:      [CORPORATE SEAL OF DELAWARE KYPHON INC. JAN. 10, 1994]

NEED FACSIMILE SIGNATURE                           NEED FACSIMILE SIGNATURE

CHIEF FINANCIAL OFFICER                    PRESIDENT AND CHIEF EXECUTIVE OFFICER

COUNTERSIGNED AND REGISTERED:

 CHASEMELLON SHAREHOLDER SERVICES, LLC.
               TRANSFER AGENT AND REGISTRAR

BY

                   AUTHORIZED SIGNATURE
<PAGE>

                                  KYPHON INC.

     A statement of all of the powers, designations, preferences and relative,
participating, optional, or other special rights of each class of stock or
series thereof and the qualifications, limitations or restrictions of such
preferences and/or rights as established by the Certificate of Incorporation, as
amended, may be obtained by any stockholder upon request and without charge from
the principal office of the Corporation.

     The following abbreviations, when used in the inscription on the face of
this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
<S>                                           <C>
TEN COM - as tenants in common                UNIF GIFT MIN ACT - __________Custodian _________________
TEN ENT - as tenants by the entireties                              (Cust)               (Minor)
JT TEN  - as joint tenants with                              under Uniform Gifts to Minors
          right of survivorship
          and not as tenants in                                   Act _________________________________
          common                                                                (State)

                                              UNIF TRF MIN ACT- ________Custodian ( until age ________)
                                                                 (Cust)

                                                               _________________under Uniform Transfers
                                                                    (Minor)

                                                               to Minors Act __________________________
                                                                                    (State)

</TABLE>
Additional abbreviations may also be used though not in the above list.

                                  ASSIGNMENT
                                  ----------

For Value Received _________________________hereby sell(s), assign(s) and
transfer(s) unto

PLEASE INSERT SOCIAL SECURITY NUMBER OR OTHER
      IDENTIFYING NUMBER OF ASSIGNEE
[                                            ]

_______________________________________________________________________________
(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE OF ASSIGNEE(S)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________
of the Shares of capital stock represented by the within Certificate and do(es)
hereby irrevocably constitute and

appoint________________________________________________________________Attorney

to transfer the said Shares on the books of the within named Corporation with
full power of substitution in the premises.

Dated _________________                     ___________________________________

                                            ___________________________________
                                            NOTE: The signature to this
                                            assignment must correspond with the
                                            names as written upon the face of
                                            the certificate in every particular,
                                            without alteration or enlargement or
                                            any change whatever. Signature must
                                            be guaranteed.

Signature(s) Guaranteed:

By ___________________________________________________________________________
THE SIGNATURES MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS,
STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP
IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM) PURSUANT TO S.E.C. RULE
17Ad-15.

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00016-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00016-of-00352.parquet"}]]