
<PAGE>   1
                                                                   EXHIBIT 10.11


                                                                      No. PBW-__

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR INVESTMENT
AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
SECURITIES LAWS. SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE
OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT AND ANY APPLICABLE
STATE SECURITIES LAWS.

THIS WARRANT AND THE SHARES PURCHASABLE HEREUNDER ARE SUBJECT TO RESTRICTIONS ON
TRANSFER CONTAINED IN THAT CERTAIN STERITECH, INC. NOTE AND WARRANT PURCHASE
AGREEMENT, DATED MAY 14, 1993, WHICH RESTRICTIONS ON TRANSFER ARE INCORPORATED
BY REFERENCE.

                        WARRANT TO PURCHASE A MAXIMUM OF
                __________ SHARES OF SERIES B PREFERRED STOCK OF
                                 STERITECH, INC.
                            (Void after May 14, 1998)

      This certifies that ___________________ (the "Holder"), or assigns, for
value received, is entitled to purchase from Steritech, Inc., a California
corporation (the "Company"), having a place of business at 2525 Stanwell Drive,
Concord, California 94520, a maximum of ________ fully paid and nonassessable
shares of the Company's Series C Preferred Stock ("Preferred Stock") for cash at
a price of ______ ($.__) per share (the "Stock Purchase Price") at any time or
from time to time up to and including 5:00 p.m. (Pacific time) on the earlier of
(i) the closing of the initial public offering of the Company's Common Stock
pursuant to a registration statement under the Securities Act of 1933, as
amended, (ii) May 14, 1998, such earlier day being referred to herein as the
"Expiration Date", upon surrender to the Company at its principal office (or at
such other location as the Company may advise the Holder in writing) of this
Warrant properly endorsed with the Form of Subscription attached hereto duly
filled in and signed and, if applicable, upon payment in cash or by check of the
aggregate Stock Purchase Price for the number of shares for which this Warrant
is being exercised determined in accordance with the provisions hereof. The
Stock Purchase Price and the number of shares purchasable hereunder are subject
to adjustment as provided in Section 3 of this Warrant. The Preferred Stock to
be issued upon exercise or conversion of this Warrant will be authorized prior
to the closing of the Company's Series C Preferred Stock financing anticipated
to occur on or before August 31, 1993. If such financing does not occur by such
date or within sixty (60) days thereafter, at Holder's request, this Warrant
shall become a warrant to purchase the Company's Series B Preferred Stock at an
exercise price of $5.065 per share and the Company will use reasonable diligent
efforts to authorize and reserve


                                       1.
<PAGE>   2
Series B Preferred Stock in sufficient amounts to cover the exercise of this
Warrant. In such event, the term "Preferred Stock" shall refer to such Series B
Preferred Stock.

This Warrant is subject to the following terms and conditions:

1.    EXERCISE; ISSUANCE OF CERTIFICATES; PAYMENT FOR SHARES.

      1.1 GENERAL. This Warrant is exercisable at the option of the holder of
record hereof, at any time or from time to time, up to the Expiration Date for
all or any part of the shares of Preferred Stock (but not for a fraction of a
share) which may be purchased hereunder. The Company agrees that the shares of
Preferred Stock purchased under this Warrant shall be and are deemed to be
issued to the Holder hereof as the record owner of such shares as of the close
of business on the date on which this Warrant shall have been surrendered,
properly endorsed, the completed, executed Form of Subscription delivered and
payment made for such shares. Certificates for the shares of Preferred Stock so
purchased, together with any other securities or property to which the Holder
hereof is entitled upon such exercise, shall be delivered to the Holder hereof
by the Company at the Company's expense within a reasonable time after the
rights represented by this Warrant have been so exercised. In case of a purchase
of less than all the shares which may be purchased under this Warrant, the
Company shall cancel this Warrant and execute and deliver a new Warrant or
Warrants of like tenor for the balance of the shares purchasable under the
Warrant surrendered upon such purchase to the Holder hereof within a reasonable
time. Each stock certificate so delivered shall be in such denominations of
Preferred Stock as may be requested by the Holder hereof and shall be registered
in the name of such Holder.

      1.2 NET ISSUE EXERCISE. Notwithstanding any provisions herein to the
contrary, if the fair market value of one share of the Company's Preferred Stock
is greater than the Stock Purchase Price (at the date of calculation as set
forth below), in lieu of exercising this Warrant for cash, the Holder may elect
to receive shares equal to the value (as determined below) of this Warrant (or
the portion thereof being canceled) by surrender of this Warrant at the
principal office of the Company together with the properly endorsed Form of
Subscription and notice of such election in which event the Company shall issue
to the Holder a number of shares of Preferred Stock computed using the following
formula:

                Y (A-B)
            X = -------
                   A

Where X =   the number of shares of Preferred Stock to be issued to the Holder

              Y = the number of shares of Preferred Stock purchasable under
                  the Warrant or, if only a portion of the Warrant is being
                  exercised, the portion of the Warrant being canceled (at the
                  date of such calculation)


                                       2.
<PAGE>   3
              A = the fair market value of one share of the Company's
                  Preferred Stock (at the date of such calculation)

              B = Stock Purchase Price (as adjusted to the date of such
                  calculation)

For purposes of the above calculation, fair market value of one share of
Preferred Stock shall be determined by the Company's Board of Directors in good
faith; provided, however, that in the event the Company makes an initial public
offering of its Common Stock the fair market value per share shall be the
product of (i) the per share offering price to the public of the Company's
initial public offering, and (ii) the number of shares of Common Stock into
which each share of Preferred Stock is convertible at the time of such exercise.

      2. SHARES TO BE FULLY PAID; RESERVATION OF SHARES. The Company covenants
and agrees that all shares of Preferred Stock which may be issued upon the
exercise of the rights represented by this Warrant will, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable and free from all
preemptive rights of any shareholder and free of all taxes, liens and charges
with respect to the issue thereof. The Company further covenants and agrees
that, except as noted in the last two sentences of the introductory paragraph of
this Warrant, during the period within which the rights represented by this
Warrant may be exercised, the Company will at all times have authorized and
reserved, for the purpose of issue or transfer upon exercise of the subscription
rights evidenced by this Warrant, a sufficient number of shares of authorized
but unissued Preferred Stock, or other securities and property, when and as
required to provide for the exercise of the rights represented by this Warrant.
The Company will take all such action as may be necessary to assure that such
shares of Preferred Stock may be issued as provided herein without violation of
any applicable law or regulation, or of any requirements of any domestic
securities exchange upon which the Preferred Stock may be listed; provided,
however, that the Company shall not be required to effect a registration under
Federal or State securities laws with respect to such exercise. The Company will
not take any action which would result in any adjustment of the Stock Purchase
Price (as defined in Section 3 hereof) (i) if the total number of shares of
Preferred Stock issuable after such action upon exercise of all outstanding
warrants, together with all shares of Preferred Stock then outstanding and all
shares of Preferred Stock then issuable upon exercise of all options and upon
the conversion of all convertible securities then outstanding, would exceed the
total number of shares of Preferred Stock then authorized by the Company's
Articles of Incorporation, or (ii) if the total number of shares of Common Stock
issuable after such action upon the conversion of all such shares of Preferred
Stock, together with all shares of Common Stock then issuable upon exercise of
all options and upon the conversion of all such shares of Preferred Stock,
together with all shares of Common Stock then outstanding and all shares of
Common Stock then issuable upon exercise of all options and upon the conversion
of all convertible securities then outstanding would exceed the total number of
shares of Common Stock then authorized by the Company's Articles of
Incorporation.


                                       3.
<PAGE>   4
      3. ADJUSTMENT OF STOCK PURCHASE PRICE AND NUMBER OF SHARES. The Stock
Purchase Price and the number of shares purchasable upon the exercise of this
Warrant shall be subject to adjustment from time to time upon the occurrence of
certain events described in this Section 3. Upon each adjustment of the Stock
Purchase Price, the Holder of this Warrant shall thereafter be entitled to
purchase, at the Stock Purchase Price resulting from such adjustment, the number
of shares obtained by multiplying the Stock Purchase Price in effect immediately
prior to such adjustment by the number of shares purchasable pursuant hereto
immediately prior to such adjustment, and dividing the product thereof by the
Stock Purchase Price resulting from such adjustment.

            3.1 SUBDIVISION OR COMBINATION OF STOCK. In case the Company shall
at any time subdivide its outstanding shares of Preferred Stock into a greater
number of shares, the Stock Purchase Price in effect immediately prior to such
subdivision shall be proportionately reduced, and conversely, in case the
outstanding shares of Preferred Stock of the Company shall be combined into a
smaller number of shares, the Stock Purchase Price in effect immediately prior
to such combination shall be proportionately increased.

            3.2   DIVIDENDS IN PREFERRED STOCK, OTHER STOCK, PROPERTY,
RECLASSIFICATION. If at any time or from time to time the Holders of Preferred
Stock (or any shares of stock or other securities at the time receivable upon
the exercise of this Warrant) shall have received or become entitled to receive,
without payment therefor,

                  (A) Preferred Stock or any shares of stock or other securities
which are at any time directly or indirectly convertible into or exchangeable
for Preferred Stock, or any rights or options to subscribe for, purchase or
otherwise acquire any of the foregoing by way of dividend or other distribution,

                  (B) any cash paid or payable otherwise than as a cash
dividend, or

                  (C) Preferred Stock or additional stock or other securities or
property (including cash) by way of spinoff, split-up, reclassification,
combination of shares or similar corporate rearrangement, (other than (i) shares
of Preferred Stock issued as a stock split, adjustments in respect of which
shall be covered by the terms of Section 3.1 above or (ii) an event for which
adjustment is otherwise made pursuant to Section 3.4 below), then and in each
such case, the Holder hereof shall, upon the exercise of this Warrant, be
entitled to receive, in addition to the number of shares of Preferred Stock
receivable thereupon, and without payment of any additional consideration
therefor, the amount of stock and other securities and property (including cash
in the cases referred to in clauses (B) and (C) above) which such Holder would
hold on the date of such exercise had he been the holder of record of such
Preferred Stock as of the date on which holders of Preferred Stock received or
became entitled to receive such shares or all other additional stock and other
securities and property.


                                       4.
<PAGE>   5
            3.3 REORGANIZATION, RECLASSIFICATION, CONSOLIDATION, MERGER OR SALE.
If any capital reorganization of the capital stock of the Company, or any
consolidation or merger of the Company with another corporation, or the sale of
all or substantially all of its assets to another corporation shall be effected
in such a way that holders of Preferred Stock shall be entitled to receive
stock, securities, or other assets or property, then, as a condition of such
reorganization, reclassification, consolidation, merger or sale, lawful and
adequate provisions shall be made whereby the holder hereof shall thereafter
have the right to purchase and receive (in lieu of the shares of the Preferred
Stock of the Company immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby) such shares of stock, securities or
other assets or property as may be issued or payable with respect to or in
exchange for a number of outstanding shares of such Preferred Stock equal to the
number of shares of such stock immediately theretofore purchasable and
receivable upon the exercise of the rights represented hereby; provided,
however, that in the event the value of the stock, securities or other assets or
property (determined in good faith by the Board of Directors of the Company)
issuable or payable with respect to one share of the Preferred Stock of the
Company immediately theretofore purchasable and receivable upon the exercise of
the rights represented hereby is in excess of the Stock Purchase Price hereof
effective at the time of the merger and securities received in such
reorganization, if any, are publicly traded, then this Warrant shall expire
unless exercised prior to the reorganization. In any reorganization described
above, appropriate provision shall be made with respect to the rights and
interests of the Holder of this Warrant to the end that the provisions hereof
(including, without limitation, provisions for adjustments of the Stock Purchase
Price and of the number of shares purchasable and receivable upon the exercise
of this Warrant) shall thereafter be applicable, as nearly as may be, in
relation to any shares of stock, securities or assets thereafter deliverable
upon the exercise hereof. The Company will not effect any such consolidation,
merger or sale unless, prior to the consummation thereof, the successor
corporation (if other than the Company) resulting from such consolidation or the
corporation purchasing such assets shall assume by written instrument, executed
and mailed or delivered to the registered Holder hereof at the last address of
such Holder appearing on the books of the Company, the obligation to deliver to
such Holder such shares of stock, securities or assets as, in accordance with
the foregoing provisions, such Holder may be entitled to purchase.

            3.4 ADJUSTMENTS SET FORTH IN ARTICLES OF INCORPORATION. In addition
to the foregoing adjustments, the conversion rate of the Series C Preferred
Stock into Common Stock is subject to adjustments as set forth in the Company's
Articles of Incorporation. The Company represents that as of the date this
Warrant was first issued, each share of Series C Preferred Stock was convertible
into one share of Common Stock.

            3.5 NOTICE OF ADJUSTMENT. Upon any adjustment of the Stock Purchase
Price or in the conversion ratio of the Series C Preferred Stock or any increase
or decrease in the number of shares purchasable upon the exercise of this
Warrant, the Company shall give written notice thereof, by first class mail,
postage prepaid, addressed to the registered Holder of this Warrant at the
address of such Holder as shown on the books of the Company.


                                       5.
<PAGE>   6
The notice shall be signed by the Company's chief financial officer and shall
state the Stock Purchase Price resulting from such adjustment and the increase
or decrease, if any, in the number of shares purchasable at such price upon the
exercise of this Warrant, setting forth in reasonable detail the method of
calculation and the facts upon which such calculation is based.

            3.6   OTHER NOTICES.   If at any time:

                  (1) the Company shall declare any cash dividend upon its
Preferred Stock;

                  (2) the Company shall declare any dividend upon its Preferred
Stock payable in stock or make any special dividend or other distribution to the
holders of its Preferred Stock;

                  (3) the Company shall offer for subscription pro rata to the
holders of its Preferred Stock any additional shares of stock of any class or
other rights;

                  (4) there shall be any capital reorganization or
reclassification of the capital stock of the Company; or consolidation or merger
of the Company with, or sale of all or substantially all of its assets to,
another corporation;

                  (5) there shall be a voluntary or involuntary dissolution,
liquidation or winding-up of the Company; or

                  (6) there shall be an initial public offering of Company
securities;

then, in any one or more of said cases, the Company shall give, by first class
mail, postage prepaid, addressed to the Holder of this Warrant at the address of
such Holder as shown on the books of the Company, (a) at least thirty (30) days'
prior written notice of the date on which the books of the Company shall close
or a record shall be taken for such dividend, distribution or subscription
rights or for determining rights to vote in respect of any such reorganization,
reclassification, consolidation, merger, sale, dissolution, liquidation or
winding-up, and (b) in the case of any such reorganization, reclassification,
consolidation, merger, sale, dissolution, liquidation, winding-up or public
offering, at least thirty (30) days' prior written notice of the date when the
same shall take place; provided, however, that the Holder shall make a best
efforts attempt to respond to such notice as early as possible after the receipt
thereof. Any notice given in accordance with the foregoing clause (a) shall also
specify, in the case of any such dividend, distribution or subscription rights,
the date on which the holders of Preferred Stock shall be entitled thereto. Any
notice given in accordance with the foregoing clause (b) shall also specify the
date on which the holders of Preferred Stock shall be entitled to exchange their
Preferred Stock for securities or other property deliverable upon such
reorganization, reclassification, consolidation, merger, sale, dissolution,
liquidation, winding-up, conversion or public offering, as the case may be.


                                       6.
<PAGE>   7
            3.7 CERTAIN EVENTS. If any change in the outstanding Preferred Stock
of the Company or any other event occurs as to which the other provisions of
this Section 3 are not strictly applicable or if strictly applicable would not
fairly protect the purchase rights of the Holder of the Warrant in accordance
with such provisions, then the Board of Directors of the Company shall make an
adjustment in the number and class of shares available under the Warrant, the
Stock Purchase Price or the application of such provisions, so as to protect
such purchase rights as aforesaid. The adjustment shall be such as will give the
Holder of the Warrant upon exercise for the same aggregate Stock Purchase Price
the total number, class and kind of shares as he would have owned had the
Warrant been exercised prior to the event and had he continued to hold such
shares until after the event requiring adjustment.

      4. ISSUE TAX. The issuance of certificates for shares of Preferred Stock
upon the exercise of the Warrant shall be made without charge to the Holder of
the Warrant for any issue tax (other than any applicable income taxes) in
respect thereof; provided, however, that the Company shall not be required to
pay any tax which may be payable in respect of any transfer involved in the
issuance and delivery of any certificate in a name other than that of the then
Holder of the Warrant being exercised.

      5. CLOSING OF BOOKS. The Company will at no time close its transfer books
against the transfer of any warrant or of any shares of Preferred Stock issued
or issuable upon the exercise of any warrant in any manner which interferes with
the timely exercise of this Warrant.

      6. NO VOTING OR DIVIDEND RIGHTS; LIMITATION OF LIABILITY. Nothing
contained in this Warrant shall be construed as conferring upon the holder
hereof the right to vote or to consent or to receive notice as a shareholder of
the Company or any other matters or any rights whatsoever as a shareholder of
the Company. No dividends or interest shall be payable or accrued in respect of
this Warrant or the interest represented hereby or the shares purchasable
hereunder until, and only to the extent that, this Warrant shall have been
exercised. No provisions hereof, in the absence of affirmative action by the
holder to purchase shares of Preferred Stock, and no mere enumeration herein of
the rights or privileges of the holder hereof, shall give rise to any liability
of such holder for the Stock Purchase Price or as a shareholder of the Company,
whether such liability is asserted by the Company or by its creditors.

      7. REGISTRATION RIGHTS AGREEMENT. The registration rights of the Holder
(including Holders' successors) with respect to this Warrant and the underlying
stock will be the same as granted to the holders of the Company's Preferred
Stock.

      8. WARRANTS TRANSFERABLE. Subject to compliance with applicable federal
and state securities laws and the transfer restrictions set forth in the Note
and Warrant Purchase Agreement dated as of May 14, 1993, under which this
Warrant was purchased, this Warrant


                                       7.
<PAGE>   8
and all rights hereunder are transferable, in whole or in part, without charge
to the holder hereof (except for transfer taxes), upon surrender of this Warrant
properly endorsed and compliance with the provisions of the Warrant Purchase
Agreement. Each taker and holder of this Warrant, by taking or holding the same,
consents and agrees that this Warrant, when endorsed in blank, shall be deemed
negotiable, and that the holder hereof, when this Warrant shall have been so
endorsed, may be treated by the Company, at the Company's option, and all other
persons dealing with this Warrant as the absolute owner hereof for any purpose
and as the person entitled to exercise the rights represented by this Warrant,
or to the transfer hereof on the books of the Company any notice to the contrary
notwithstanding; but until such transfer on such books, the Company may treat
the registered owner hereof as the owner for all purposes.

      9. RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT. The rights and
obligations of the Company, of the holder of this Warrant and of the holder of
shares of Preferred Stock issued upon exercise of this Warrant, referred to in
Sections 7 and 8 shall survive the exercise of this Warrant.

      10. MODIFICATION AND WAIVER. This Warrant and any provision hereof may be
changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought, provided
that any change, waiver, discharge or termination agreed to in writing by a
majority in interest of holders of Warrants of the Company of even date issued
pursuant to the Note and Warrant Purchase Agreement shall be binding on Holder
and assigns.

      11. NOTICES. Any notice, request or other document required or permitted
to be given or delivered to the holder hereof or the Company shall be delivered
or shall be sent by certified mail, postage prepaid, to each such holder at its
address as shown on the books of the Company or to the Company at the address
indicated therefor in the first paragraph of this Warrant or such other address
as either may from time to time provide to the other.

      12. BINDING EFFECT ON SUCCESSORS. This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets. All of the obligations of the
Company relating to the Preferred Stock issuable upon the exercise of this
Warrant shall survive the exercise and termination of this Warrant. All of the
covenants and agreements of the Company shall inure to the benefit of the
successors and assigns of the holder hereof.

      13. DESCRIPTIVE HEADINGS AND GOVERNING LAW. The description headings of
the several sections and paragraphs of this Warrant are inserted for convenience
only and do not constitute a part of this Warrant. This Warrant shall be
construed and enforced in accordance with, and the rights of the parties shall
be governed by, the laws of the State of California.


                                       8.
<PAGE>   9
      14. LOST WARRANTS. The Company represents and warrants to the Holder
hereof that upon receipt of evidence reasonably satisfactory to the Company of
the loss, theft, destruction, or mutilation of this Warrant and, in the case of
any such loss, theft or destruction, upon receipt of an indemnity reasonably
satisfactory to the Company, or in the case of any such mutilation upon
surrender and cancellation of such Warrant, the Company, at its expense, will
make and deliver a new Warrant, of like tenor, in lieu of the lost, stolen,
destroyed or mutilated Warrant.

      15. FRACTIONAL SHARES. No fractional shares shall be issued upon exercise
of this Warrant. The Company shall, in lieu of issuing any fractional share, pay
the holder entitled to such fraction a sum in cash equal to such fraction
multiplied by the then effective Stock Purchase Price.

      IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed by its officers, thereunto duly authorized this 14th day of May, 1993.

                                          STERITECH, INC.
                                          A CALIFORNIA CORPORATION

                                          By____________________________________

                                          Title_________________________________

ATTEST:

______________________________
Secretary


                                       9.
<PAGE>   10
                                    EXHIBIT A

                                SUBSCRIPTION FORM

                                                       Date:  ____________, 19__

Steritech, Inc.
2525 Stanwell Drive
Concord, California  94520

Gentlemen:

[ ]   The undersigned hereby elects to exercise the warrant issued to it by
      Steritech, Inc. (the "Company") and dated May 14, 1993 Warrant No. PBW-__
      (the "Warrant") and to purchase thereunder ____________ shares of the
      Common Stock of the Company (the "Shares") at a purchase price of
      _________________________________________ ($_____) per Share or an
      aggregate purchase price of __________________________ Dollars ($______)
      (the "Purchase Price").

[ ]   The undersigned hereby elects to convert ______________________ percent
      (__%) of the value of the Warrant pursuant to the provisions of Section
      1.2 of the Warrant.

      Pursuant to the terms of the Warrant the undersigned has delivered the
Purchase Price herewith in full in cash or by certified check or wire transfer.
The undersigned also makes the representations set forth on the attached Exhibit
B of the Warrant.

                                          Very truly yours,

                                          _____________________________

                                          By____________________________________

                                          Title_________________________________


                                       1.
<PAGE>   11
                                    EXHIBIT B

                           INVESTMENT REPRESENTATIONS

THIS AGREEMENT MUST BE COMPLETED, SIGNED AND RETURNED TO STERITECH, INC. ALONG
WITH THE SUBSCRIPTION FORM BEFORE THE COMMON STOCK ISSUABLE UPON EXERCISE OF THE
WARRANT CERTIFICATE DATED ____________, 1993, WILL BE ISSUED.

                           _____________________, 19__

Steritech, Inc.
2525 Stanwell Drive
Concord, California  94520

Attention: President

      The undersigned,_____("Purchaser"), intends to acquire up to shares of the
Series B Preferred Stock (the "Preferred Stock") of Steritech, Inc. (the
"Company") from the Company pursuant to the exercise or conversion of certain
Warrants to purchase Preferred Stock held by Purchaser. The Preferred Stock will
be issued to Purchaser in a transaction not involving a public offering and
pursuant to an exemption from registration under the Securities Act of 1933, as
amended (the "1933 Act") and applicable state securities laws. In connection
with such purchase and in order to comply with the exemptions from registration
relied upon by the Company, Purchaser represents, warrants and agrees as
follows:

      Purchaser is acquiring the Preferred Stock for its own account, to hold
for investment, and Purchaser shah not make any sale, transfer or other
disposition of the Preferred Stock in violation of the 1933 Act or the General
Rules and Regulations promulgated thereunder by the Securities and Exchange
Commission (the "SEC") or in violation of any applicable state securities law.

      Purchaser has been advised that the Preferred Stock has not been
registered under the 1933 Act or state securities laws on the ground that this
transaction is exempt from registration, and that reliance by the Company on
such exemptions is predicated in pan on Purchaser's representations set forth in
this letter.

      Purchaser has been informed that under the 1933 Act, the Preferred Stock
must be held indefinitely unless it is subsequently registered under the 1933
Act or unless an exemption from such registration (such as Rule 144) is
available with respect to any proposed transfer or disposition by Purchaser of
the Preferred Stock. Purchaser further agrees that the Company


                                       1.
<PAGE>   12
may refuse to permit Purchaser to sell, transfer or dispose of the Preferred
Stock (except as permitted under Rule 144) unless there is in effect a
registration statement underthe 1933 Act and any applicable state securities
laws coveting such transfer, or unless Purchaser furnishes an opinion of counsel
reasonably satisfactory to counsel for the Company, to the effect that such
registration is not required.

      Purchaser also understands and agrees that there will be placed on the
certificate(s) for the Preferred Stock, or any substitutions therefor, a legend
stating in substance:

            "The shares represented by this certificate have not been registered
      under the Securities Act of 1933, as amended (the "Securities Act"), or
      any state securities laws. These shares have been acquired for investment
      and may not be sold or otherwise transferred in the absence of an
      effective registration statement for these shares under the Securities Act
      and applicable state securities laws, or an opinion of counsel
      satisfactory to the Company that registration is not required and that an
      applicable exemption is available."

      Purchaser has carefully read this letter and has discussed its
requirements and other applicable limitations upon Purchaser's resale of the
Preferred Stock with Purchaser's counsel.

                                          Very truly yours,

                                          ______________________________

                                          By:___________________________________


                                       2.
