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                                                                     EXHIBIT 4.5

THE REPRESENTATIVE'S OPTION REPRESENTED BY THIS CERTIFICATE AND THE SECURITIES
ISSUABLE UPON EXERCISE HEREOF (THE "SECURITIES") HAVE BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED, PURSUANT TO A REGISTRATION STATEMENT FILED
WITH THE SECURITIES AND EXCHANGE COMMISSION AND WITH THE SECURITIES
ADMINISTRATORS OF CERTAIN STATES UNDER THE SECURITIES ("BLUE SKY") LAWS OF SUCH
STATES. HOWEVER, NEITHER THE REPRESENTATIVE'S OPTION NOR SUCH SECURITIES MAY BE
SOLD, TRANSFERRED, PLEDGED, OR HYPOTHECATED EXCEPT PURSUANT TO (i) A
POST-EFFECTIVE AMENDMENT TO SUCH REGISTRATION STATEMENT, (ii) A SEPARATE
REGISTRATION STATEMENT UNDER SUCH ACT, OR (iii) AN EXEMPTION FROM REGISTRATION
UNDER SUCH ACT AND UNDER THE APPLICABLE BLUE SKY LAWS.

THIS REPRESENTATIVE'S OPTION MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED EXCEPT AS
OTHERWISE PROVIDED HEREIN AND THE HOLDER OF THIS REPRESENTATIVE'S OPTION, BY ITS
ACCEPTANCE HEREOF, AGREES THAT IT WILL NOT SELL, TRANSFER OR ASSIGN THIS
REPRESENTATIVE'S OPTION EXCEPT AS OTHERWISE PROVIDED HEREIN.

                        NATURAL GAS SERVICES GROUP, INC.

              REPRESENTATIVE'S OPTION FOR THE PURCHASE OF WARRANTS

NO. UWW-001                                     165,000 REPRESENTATIVE'S OPTIONS

         THIS CERTIFIES that, for receipt in hand of $50 and other value
received (the "Purchase Price"), NEIDIGER, TUCKER, BRUNER, INC. (the "Holder"),
is entitled to subscribe for and purchase from NATURAL GAS SERVICES GROUP, INC.,
a Colorado corporation (the "Company"), upon the terms and conditions set forth
herein, at any time, or from time to time, after _______________, 2003 (12
months from the Effective Date, as defined below) and before 5:00 p.m. Colorado
time on _______________, 2007 (the "Exercise Period"), 165,000 Warrants (a
"Warrant" or the "Warrants") of the Company at an exercise price of $______ per
Representative's Option or 125% of the offering price of Warrants sold by the
Company in the Public Offering (hereinafter defined). Subject to the higher
exercise price and the longer exercise period set forth below each Warrant shall
be identical to the Warrants sold in the public offering to be underwritten by
the Holder (the "Public Offering"). Each Warrant shall be exercisable to
purchase one share of Common Stock (a "Warrant Share") at a price of $__________
(125% of the exercise price of the Warrants sold in the Public Offering; the
"Exercise Price") until _______________, 2008, which is six years from the date
on which the Company's Registration Statement on Form SB-2, Registration No.
333-88314 (the

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"Registration Statement") was declared effective by the Securities and Exchange
Commission (the "Effective Date").

         The term the "Holder" as used herein shall include any transferee to
whom this Representative's Option has been transferred in accordance with the
terms of this Representative's Option. As used herein the term "this
Representative's Option" shall mean and include this Representative's Option and
any Representative's Option or Representative's Options hereafter issued as a
consequence of the exercise or transfer of this Representative's Option in whole
or in part, but shall exclude the Warrants, and the term "Common Stock" shall
mean and include the Company's Common Stock with ordinary voting power, which
class at the date hereof is publicly traded.

         1. This Representative's Option may not be sold, transferred, assigned,
pledged or hypothecated until ______________, 2003 (12 months from the Effective
Date of the Registration Statement) except that it may be transferred, in whole
or in part, (i) to one or more officers or partners of the Holder (or the
officers or partners of any such partner); (ii) to a member of the underwriting
syndicate and/or its officers or partners; or (iii) by operation of law. After
_________, 2003, this Representative's Option may be sold, transferred, assigned
or hypothecated in accordance with applicable law.

         2. (a) This Representative's Option may be exercised during the
         Exercise Period as to the whole or any lesser number of Warrants, by
         the surrender of this Representative's Option (with the election
         attached hereto duly executed) to the Company at its office at 2911
         South County Road 1260, Midland, Texas 79706, or such other place as is
         designated in writing by the Company, together with a certified or bank
         cashier's check payable to the order of the Company in an amount equal
         to the Purchase Price.

                  (b) Following exercise of this Representative's Option, and at
         anytime thereafter through and until expiration of the Warrants, the
         Holder may exercise the Warrants underlying this Representative's
         Option by tendering a notice of exercise, together with a certified or
         bank cashier's check payable to the order of the Company, in

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         an amount equal to the Exercise Price multiplied by the number of
         Warrant Shares as to which such exercise relates.

                  (c) Upon written request of the Holder, and in lieu of payment
         of the Exercise Price of the Warrants by check in accordance with
         paragraph 2(b) hereof, the Holder may exercise the Warrants (or any
         portion thereof) for and receive the number of Warrants equal to a
         fraction, the numerator of which equals (i) the amount by which the
         Current Market Price of the Common Stock for the ten (10) trading days
         preceding the date of exercise exceeds the Exercise Price per Warrant,
         multiplied by (ii) the number of Warrant Shares to be purchased; the
         denominator of which equals the Current Market Price.

                  (d) For the purposes of any computation under this
         Representative's Option, the "Current Market Price" at any date shall
         be the closing price of the Common Stock on the business day next
         preceding the event requiring an adjustment hereunder. If the principal
         trading market for such securities is an exchange, the closing price
         shall be the reported last sale price on such exchange on such day
         provided if trading of such Common Stock is listed on any consolidated
         tape, the closing price shall be the reported last sale price set forth
         on such consolidated tape. If the principal trading market for such
         securities is the over-the-counter market, the closing price shall be
         the last reported sale price on such date as set forth by The Nasdaq
         Stock Market, Inc., or, if the security is not quoted on such market,
         the average closing bid and asked prices as set forth in the National
         Quotation Bureau pink sheet or the Electronic Bulletin Board System for
         such day. Notwithstanding the foregoing, if there is no reported last
         sale price or average closing bid and asked prices, as the case may be,
         on a date prior to the event requiring an adjustment hereunder, then
         the Current Market Price shall be determined as of the latest date
         prior to such day for which such last sale price or average closing bid
         and asked price is available.

         3. Upon each exercise of this Representative's Option, the Holder shall
be deemed to be the holder of record of the Warrants issuable upon such
exercise, notwithstanding that the transfer books of the Company shall then be
closed or certificates representing such Warrants shall not then have been
actually delivered to the Holder. As soon as practicable after each such

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exercise of this Representative's Option, the Company shall issue and deliver to
the Holder a certificate or certificates for the Warrants issuable upon such
exercise, registered in the name of the Holder or its designee. If this
Representative's Option should be exercised in part only, the Company shall,
upon surrender of this Representative's Option for cancellation, execute and
deliver a new Representative's Option evidencing the right of the Holder to
purchase the balance of the Warrants (or portions thereof) subject to purchase
hereunder.

         4. Any warrants, other than the Warrants, issued upon the transfer or
exercise in part of this Representative's Option (together with this
Representative's Option, the "Representative's Options") shall be numbered and
shall be registered in a Representative's Option Register as they are issued.
The Company shall be entitled to treat the registered holder of any
Representative's Option on the Representative's Option Register as the owner in
fact thereof for all purposes and shall not be bound to recognize any equitable
or other claim to or interest in such Representative's Option on the part of any
other person. The Representative's Options shall be transferable only on the
books of the Company upon delivery thereof duly endorsed by the Holder or by his
duly authorized attorney or representative, or accompanied by proper evidence of
succession, assignment or authority to transfer. In all cases of transfer by an
attorney, executor, administrator, guardian or other legal representative, duly
authenticated evidence of his or its authority shall be produced. Upon any
registration of transfer, the Company shall deliver a new Representative's
Option or Representative's Options to the person entitled thereto. The
Representative's Options may be exchanged, at the option of the Holder thereof,
for another Representative's Option, or other Representative's Options of
different denominations, of like tenor and representing in the aggregate the
right to purchase a like number of Warrants (or portions thereof) upon surrender
to the Company or its duly authorized agent. Notwithstanding the foregoing, the
Company shall have no obligation to cause Representative's Options to be
transferred on its books to any person if, in the opinion of counsel to the
Company, such transfer does not comply with the provisions of the Securities Act
of 1933, as amended (the "Act"), or applicable state blue sky laws and the rules
and regulations thereunder.

         5. The Company shall at all times reserve and keep available out of its
authorized and unissued Common Stock, solely for the purpose of providing for
the exercise of this Representative's Option and the Warrants purchasable upon
exercise of this Representative's

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Option, such number of shares of Common Stock as shall, from time to time, be
sufficient therefor. The Company covenants that all shares of Common Stock
issuable upon exercise of Warrants underlying this Representative's Option shall
be validly issued, fully paid, nonassessable, and free of preemptive rights.

         6. The rights and privileges of the Warrants issuable on exercise of
this Representative's Option shall be as provided in the warrant certificate
(the "Warrant Certificate") to be delivered to the Holder on exercise of this
Representative's Option. All anti-dilution and other rights shall be as provided
for in the Warrant Certificate and as set forth in the warrant agreement by and
between the Company and the Warrant Agent for the Company (the "Warrant
Agreement"). The provisions of the Warrant Agreement relating to anti-dilution
rights and any other rights and privileges granted to holders of publicly traded
Warrants are incorporated by reference herein as if more fully set forth herein.
Notwithstanding any other language to the contrary herein or in the Warrant
Agreement by and between the Company and the Warrant Agent, in the event, prior
to the exercise of this Warrant, Holders of publicly-traded Warrants shall be
entitled to the benefit of any anti-dilution provisions of the Warrant Agreement
or the Warrant Certificate then, in such event, the Warrants issuable upon
exercise of this Representative's Option shall be adjusted in accordance with
the provisions of the anti-dilution provisions of the Warrant Certificate and
the Warrant Agreement in a manner identical to the adjustments made pursuant to
the anti-dilution provisions and other rights and privileges applicable to
publicly-traded warrants. Any such adjustment may be made at or immediately
following the date of exercise hereof. Notwithstanding any other language to the
contrary herein, (i) the anti-dilution terms of this Representative's Option
will not be enforced so as to provide the Holder the right to receive, or for
the accrual of, cash dividends prior to the exercise of this Representative's
Option, and (ii) the anti-dilution terms of this Representative's Option will
not be enforced in such a manner as to provide the Holder with disproportionate
rights, privileges and economic benefits not provided to purchasers of Warrants
in the Public Offering.

         7. The issuance of any Warrants or other securities upon the exercise
of this Representative's Option or any Warrant Shares upon the exercise of the
Warrants, and the delivery of certificates or other instruments representing
such securities, or other securities, shall be made without charge to the Holder
for any tax or other charge in respect of such issuance.

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The Company shall not, however, be required to pay any tax which may be payable
in respect of any transfer involved in the issue and delivery of any certificate
in a name other than that of the Holder and the Company shall not be required to
issue or deliver any such certificate unless and until the person or persons
requesting the issue thereof shall have paid to the Company the amount of such
tax or shall have established to the satisfaction of the Company that such tax
has been paid.

         8. (a) If, at any time after ______________, 2003 (one year after the
         Effective Date of the Registration Statement), and ending
         _______________, 2008 (six years after the Effective Date of the
         Registration Statement), the Company shall file a registration
         statement (other than on Form S-4, Form S-8, or any successor form)
         with the Securities and Exchange Commission (the "Commission") while
         Warrants are available for purchase upon exercise of this
         Representative's Option or while any Warrants or Warrant Shares
         (collectively, the "Representative's Securities") are outstanding, the
         Company shall give the Holder and all the then holders of such
         Representative's Options and Representative's Securities at least 30
         days prior written notice of the filing of such registration statement.
         If requested by the Holder or by any such holder in writing within 20
         days after receipt of any such notice, the Company shall, at the
         Company's sole expense (other than the fees and disbursements of
         counsel for the Holder or such holder and the underwriting discounts
         and unaccountable expenses, if any, payable in respect of the
         securities sold by the Holder or any such holder), register or qualify
         the Representative's Securities of the Holder or any such holders who
         shall have made such request concurrently with the registration of such
         other securities, all to the extent requisite to permit the public
         offering and sale of the Representative's Securities, and will use its
         best efforts through its officers, directors, auditors and counsel to
         cause such registration statement to become effective as promptly as
         practicable. Notwithstanding the foregoing, if the managing underwriter
         of any such offering shall advise the Company in writing that, in its
         opinion, the distribution of all or a portion of the Representative's
         Securities requested to be included in the registration concurrently
         with the securities being registered by the Company would materially
         adversely affect the distribution of such securities by the Company for
         its own account, then the Holder or any such holder who shall have
         requested registration of his or its Representative's Securities shall
         delay

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         the offering and sale of such Representative's Securities (or the
         portions thereof so designated by such managing underwriter) for such
         period, not to exceed 90 days, as the managing underwriter shall
         request, provided that no such delay shall be required as to any
         Representative's Securities if any securities of the Company are
         included in such registration statement for the account of any person
         other than the Company and the Holder unless the securities included in
         such registration statement for such other person shall have been
         reduced pro rata to the reduction of the Representative's Securities
         which were requested to be included in such registration.

                  (b) If at any time after _______________, 2003 (one year after
         the Effective Date of the Registration Statement), and before
         _______________, 2007 (five years after the Effective Date of the
         Registration Statement), the Company shall receive a written request
         from holders of Representative's Securities who, in the aggregate, own
         (or upon exercise of all Representative's Options will own) a majority
         of the total number of Representative's Securities, the Company shall,
         as promptly as practicable, prepare and file with the Commission a
         registration statement sufficient to permit the public offering and
         sale of the Representative's Securities, and will use its best efforts
         through its officers, directors, auditors and counsel to cause such
         registration statement to become effective as promptly as practicable;
         provided, however, that the Company shall only be obligated to file and
         obtain effectiveness of one such registration statement for which all
         expenses incurred in connection with such registration (other than the
         fees and disbursements of counsel for the Holder or such holders and
         underwriting discounts and unaccountable expenses, if any, payable in
         respect of the Representative's Securities sold by the Holder or any
         such holder) shall be borne by the Company.

                  (c) In the event of a registration pursuant to the provisions
         of this paragraph 8, the Company shall use its best efforts to cause
         the Representative's Securities so registered to be registered or
         qualified for sale under the securities or blue sky laws of such
         jurisdictions as the Holder or such holders may reasonably request;
         provided, however, that the Company shall not be required to qualify to
         do business in any state by reason of this paragraph 8(c) in which it
         is not otherwise required to qualify to do business and provided
         further, that the Company has no obligation to qualify the

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         Representative's Securities where such qualification would cause any
         unreasonable delay or expenditure by the Company.

                  (d) The Company shall keep effective any registration or
         qualification contemplated by this paragraph 8 and shall from time to
         time amend or supplement each applicable registration statement,
         preliminary prospectus, final prospectus, application, document and
         communication for such period of time as shall be required to permit
         the Holder or such holders to complete the offer and sale of the
         Representative's Securities covered thereby. The Company shall in no
         event be required to keep any such registration or qualification in
         effect for a period in excess of nine months from the date on which the
         Holder and such holders are first free to sell such Representative's
         Securities; provided, however, that if the Company is required to keep
         any such registration or qualification in effect with respect to
         securities other than the Representative's Securities beyond such
         period, the Company shall keep such registration or qualification in
         effect as it relates to the Representative's Securities for so long as
         such registration or qualification remains or is required to remain in
         effect in respect of such other securities.

                  (e) In the event of a registration pursuant to the provisions
         of this paragraph 8, the Company shall furnish to the Holder and to
         each such holder such reasonable number of copies of the registration
         statement and of each amendment and supplement thereto (in each case,
         including all exhibits), such reasonable number of copies of each
         prospectus contained in such registration statement and each supplement
         or amendment thereto (including each preliminary prospectus), all of
         which shall conform to the requirements of the Act and the rules and
         regulations thereunder, and such other documents as the Holder or such
         holders may reasonably request in order to facilitate the disposition
         of the Representative's Securities included in such registration.

                  (f) In the event of a registration pursuant to the provisions
         of this paragraph 8, the Company shall furnish the Holder and each
         holder of any Representative's Securities so registered with an opinion
         of its counsel to the effect that the registration statement has become
         effective under the Act and no order suspending the effectiveness of
         the

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         registration statement, preventing or suspending the use of the
         registration statement, any preliminary prospectus, any final
         prospectus, or any amendment or supplement thereto has been issued, nor
         to such counsel's actual knowledge has the Securities and Exchange
         Commission or any securities or blue sky authority of any jurisdiction
         instituted or threatened to institute any proceedings with respect to
         such an order and (ii) the registration statement and each prospectus
         forming a part thereof (including each preliminary prospectus), and any
         amendment or supplement thereto, complies as to form with the Act and
         the rules and regulations thereunder. Such counsel shall also provide a
         Blue Sky Memorandum setting forth the jurisdictions in which the
         Representative's Securities have been registered or qualified for sale
         pursuant to the provisions of paragraph 8(c).

                  (g) The Company agrees that until all the Representative's
         Securities have been sold under a registration statement or pursuant to
         Rule 144 under the Act or until the Representative's Securities may be
         sold under Rule 144(k), it shall keep current in filing all reports,
         statements and other materials required to be filed with the Commission
         to permit holders of the Representative's Securities to sell such
         securities under Rule 144.

                  (h) The Holder and any holders who propose to register their
         Representative's Securities under the Act shall execute and deliver to
         the Company a selling stockholder questionnaire on a form to be
         provided by the Company.

                  (i) The Company shall not be required by the terms hereof to
         file a Registration Statement if, in the opinion of counsel to the
         holders of the Representative's Securities and counsel for the Company
         (or, should they not agree, in the opinion of another counsel
         experienced in securities law matters acceptable to counsel for the
         holders of Representative's Securities and the Company), the proposed
         public offering or other transfer as to which such Registration
         Statement is requested to be filed is exempt from applicable federal
         and state securities laws, rules, regulations and would result in
         unaffiliated purchasers or transferees obtaining securities that are
         not "restricted securities" as that term is defined in Rule 144 under
         the Act.

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         9. (a) Subject to the conditions set forth below, the Company agrees to
         indemnify and hold harmless the Holder, any holder of any of the
         Representative's Securities, their officers, directors, partners,
         employees, agents and counsel, and each person, if any, who controls
         any such person within the meaning of Section 15 of the Act or Section
         20(a) of the Securities Exchange Act of 1934, as amended (the "Exchange
         Act"), from and against any and all loss, liability, charge, claim,
         damage and expense whatsoever (which shall include, for all purposes of
         this Section 9, but not be limited to, attorneys' fees and any and all
         expense whatsoever incurred in investigating, preparing or defending
         against any litigation, commenced or threatened, or any claim
         whatsoever, and any and all amounts paid in settlement of any claim or
         litigation), as and when incurred, arising out of, based upon, or in
         connection with (i) any untrue statement or alleged untrue statement of
         a material fact contained (A) in any registration statement,
         preliminary prospectus or final prospectus (as from time to time
         amended and supplemented), or any amendment or supplement thereto, or
         (B) in any application or other document or communication (in this
         Section 9 collectively called an "application") executed by or on
         behalf of the Company or based upon written information furnished by or
         on behalf of the Company filed in any jurisdiction in order to register
         or qualify any of the Representative's Securities under the securities
         or blue sky laws thereof or filed with the Commission or any securities
         exchange; or any omission or alleged omission to state a material fact
         required to be stated therein or necessary to make the statements
         therein not misleading, unless such statement or omission was made in
         reliance upon and in conformity with written information furnished to
         the Company with respect to the Holder or any holder of any of the
         Representative's Securities by or on behalf of such person expressly
         for inclusion in any registration statement, preliminary prospectus, or
         final prospectus, or any amendment or supplement thereto, or in any
         application, as the case may be, or (ii) any breach of any
         representation, warranty, covenant or agreement of the Company
         contained in this Representative's Option. The foregoing agreement to
         indemnify shall be in addition to any liability the Company may
         otherwise have, including liabilities arising under this
         Representative's Option.

                  If any action is brought against the Holder or any holder of
         any of the Representative's Securities or any of its officers,
         directors, partners, employees, agents or

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         counsel, or any controlling persons of such person (an "indemnified
         party") in respect of which indemnity may be sought against the Company
         pursuant to the foregoing paragraph, such indemnified party or parties
         shall promptly notify the Company in writing of the institution of such
         action (but the failure so to notify shall not relieve the Company from
         any liability it may otherwise have to Holder or any holder of any of
         the Representative's Securities) and the Company shall promptly assume
         the defense of such action, including the employment of counsel
         (reasonably satisfactory to such indemnified party or parties) and
         payment of expenses. Such indemnified party or parties shall have the
         right to employ its or their own counsel in any such case, but the fees
         and expenses of such counsel shall be at the expense of such
         indemnified party or parties unless the employment of such counsel
         shall have been authorized in writing by the Company in connection with
         the defense of such action or the Company shall not have promptly
         employed counsel reasonably satisfactory to such indemnified party or
         parties to have charge of the defense of such action or such
         indemnified party or parties shall have reasonably concluded that there
         may be one or more legal defenses available to it or them or to other
         indemnified parties which are different from or additional to those
         available to the Company, in any of which events such fees and expenses
         shall be borne by the Company and the Company shall not have the right
         to direct the defense of such action on behalf of the indemnified party
         or parties. Anything in this paragraph to the contrary notwithstanding,
         the Company shall not be liable for any settlement of any such claim or
         action effected without its written consent.

                  (b) The Holder and each holder agrees to indemnify and hold
         harmless the Company, each director of the Company, each officer of the
         Company who shall have signed any registration statement covering the
         Representative's Securities held by the Holder and each holder and each
         other person, if any, who controls the Company within the meaning of
         Section 15 of the Act or Section 20(a) of the Exchange Act, to the same
         extent as the foregoing indemnity from the Company to the Holder and
         each holder in paragraph 9(a), but only with respect to statements or
         omissions, if any, made in any registration statement, preliminary
         prospectus, or final prospectus (as from time to time amended and
         supplemented), or any amendment or supplement thereto, or in any
         application, in reliance upon and in conformity with written
         information furnished to the

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         Company with respect to the Holder and each holder by or on behalf of
         the Holder and each holder expressly for inclusion in any such
         registration statement, preliminary prospectus, or final prospectus, or
         any amendment or supplement thereto, or in any application, as the case
         may be. If any action shall be brought against the Company or any other
         person so indemnified based on any such registration statement,
         preliminary prospectus, or final prospectus, or any amendment or
         supplement thereto, or in any application, and in respect of which
         indemnity may be sought against the Holder and each holder pursuant to
         this paragraph 9(b), the Holder and each holder shall have the rights
         and duties given to the Company, and the Company and each other person
         so indemnified shall have the rights and duties given to the
         indemnified parties, by the provisions of paragraph 9(a).

                  (c) To provide for just and equitable contribution, if (i) an
         indemnified party makes a claim for indemnification pursuant to
         paragraph 9(a) or 9(b) (subject to the limitations thereof) but it is
         found in a final judicial determination, not subject to further appeal,
         that such indemnification may not be enforced in such case, even though
         this Agreement expressly provides for indemnification in such case, or
         (ii) any indemnified or indemnifying party seeks contribution under the
         Act, the Exchange Act or otherwise because the indemnification provided
         for in this Section 9 is for any reason held to be unenforceable by the
         Company and the Holder and any holder, then the Company (including for
         this purpose any contribution made by or on behalf of any director of
         the Company, any officer of the Company who signed any such
         registration statement and any controlling person of the Company), as
         one entity, and the Holder and any holder of any of the
         Representative's Securities included in such registration in the
         aggregate (including for this purpose any contribution by or on behalf
         of the Holder or any holder), as a second entity, shall contribute to
         the losses, liabilities, claims, damages and expenses whatsoever to
         which any of them may be subject, on the basis of relevant equitable
         considerations such as the relative fault of the Company and the Holder
         or any such holder in connection with the facts which resulted in such
         losses, liabilities, claims, damages and expenses. The relative fault,
         in the case of an untrue statement, alleged untrue statement, omission
         or alleged omission, shall be determined by, among other things,
         whether such statement, alleged statement, omission or alleged omission

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         relates to information supplied by the Company, by the Holder or by any
         holder of Representative's Securities included in such registration,
         and the parties' relative intent, knowledge, access to information and
         opportunity to correct or prevent such statement, alleged statement,
         omission or alleged omission. The Company and the Holder agree that it
         would be unjust and inequitable if the respective obligations of the
         Company and the Holder for contribution were determined by pro rata or
         per capita allocation of the aggregate losses, liabilities, claims,
         damages and expenses (even if the Holder and the other indemnified
         parties were treated as one entity for such purpose) or by any other
         method of allocation that does not reflect the equitable considerations
         referred to in this paragraph 9(c). No person guilty of a fraudulent
         misrepresentation (within the meaning of Section 11 (f) of the Act)
         shall be entitled to contribution from any person who is not guilty of
         such fraudulent misrepresentation. For purposes of this paragraph 9(c),
         each person, if any, who controls the Holder or any holder of any of
         the Representative's Securities within the meaning of Section 15 of the
         Act or Section 20(a) of the Exchange Act and each officer, director,
         partner, employee, agent and counsel of each such person, shall have
         the same rights to contribution as such person and each person, if any,
         who controls the Company within the meaning of Section 15 of the Act or
         Section 20(a) of the Exchange Act, each officer of the Company who
         shall have signed any such registration statement, and each director of
         the Company shall have the same rights to contribution as the Company,
         subject in each case to the provisions of this paragraph 9(c). Anything
         in this paragraph 9(c) to the contrary notwithstanding, no party shall
         be liable for contribution with respect to the settlement of any claim
         or action effected without its written consent. This paragraph 9(c) is
         intended to supersede any right to contribution under the Act, the
         Exchange Act or otherwise.

         10. The securities issued upon exercise of the Representative's Options
shall be subject to a stop transfer order and the certificate or certificates
evidencing any such securities shall bear the following legend or a legend
substantially similar thereto:

         THE SECURITIES REPRESENTED BY THIS CERTIFICATE AND THE SECURITIES
         ISSUABLE UPON EXERCISE HEREOF (THE "SECURITIES") HAVE BEEN REGISTERED
         UNDER THE SECURITIES ACT OF 1933, AS AMENDED, PURSUANT TO A
         REGISTRATION STATEMENT FILED WITH THE SECURITIES AND EXCHANGE
         COMMISSION AND WITH THE SECURITIES ADMINISTRATORS OF

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         CERTAIN STATES UNDER THE SECURITIES ("BLUE SKY") LAWS OF SUCH STATES.
         HOWEVER, NEITHER THE REPRESENTATIVE'S OPTIONS NOR SUCH SECURITIES MAY
         BE SOLD, TRANSFERRED, PLEDGED, OR HYPOTHECATED EXCEPT PURSUANT TO (i) A
         POST-EFFECTIVE AMENDMENT TO SUCH REGISTRATION STATEMENT, (ii) A
         SEPARATE REGISTRATION STATEMENT UNDER SUCH ACT, OR (iii) AN EXEMPTION
         FROM REGISTRATION UNDER SUCH ACT AND UNDER THE APPLICABLE BLUE SKY
         LAWS.

         11. Upon receipt of evidence satisfactory to the Company of the loss,
theft, destruction or mutilation of any Representative's Option (and upon
surrender of any Representative's Option if mutilated), and upon reimbursement
of the Company's reasonable incidental expenses, the Company shall execute and
deliver to the Holder thereof a new Representative's Option of like date, tenor
and denomination.

         12. The Holder of any Representative's Option shall not have, solely on
account of such status, any rights of a stockholder of the Company, either at
law or in equity, or to any notice of meetings of stockholders or of any other
proceedings of the Company, except as provided in this Representative's Option.

         13. This Representative's Option shall be construed in accordance with
the laws of the State of Colorado, without giving effect to conflict of laws.

Dated:                         , 2002
      -------------------------

                                NATURAL GAS SERVICES GROUP, INC.

                                By:
                                   -------------------------------------------
                                     Wayne L. Vinson, President
 [SEAL]

                                       14
<PAGE>

                               FORM OF ASSIGNMENT

(To be executed by the registered holder if such holder desires to transfer the
attached Representative's Option.)

         FOR VALUE RECEIVED, _______________ hereby sells, assigns and transfers
unto ________________________________ Representative's Option to purchase
_____________ Warrants of Natural Gas Services Group, Inc. (the "Company"),
together with all right, title and interest therein, and does hereby irrevocably
constitute and appoint _______________________ attorney to transfer such
Representative's Option on the books of the Company, with full power of
substitution.

Dated:
      -----------------------------------------------

Signature:
          -------------------------------------------

Signature Guaranteed:

                                     NOTICE

         The signature on the foregoing Assignment must correspond to the name
as written upon the face of this Representative's Option in every particular,
without alteration or enlargement or any change whatsoever. Signature(s) must be
guaranteed by an eligible guarantor institution which is a participant in a
Securities Transfer Association recognized program.

                                       15
<PAGE>

                              ELECTION TO EXERCISE

             (To be executed by the holder if such holder desires to
                 exercise the attached Representative's Option)

         The undersigned hereby exercises his or its rights to subscribe for
______________ Warrants covered by the within Representative's Option (each as
defined in the within Representative's Option) and tenders payment herewith in
the amount of $______________ in accordance with the terms thereof, and requests
that certificates for such Warrants be issued in the name of, and delivered to:

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

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

--------------------------------------------------------------------------------
                   (Print Name, Address and Social Security or
                           Tax Identification Number)

and, if such number of Warrants (or portions thereof) shall not be all the
Warrants covered by the within Representative's Option, that a new
Representative's Option for the balance of the Representative's Options (or
portions thereof) covered by the within Representative's Option be registered in
the name of, and delivered to, the undersigned at the address stated below.

Name:
     ---------------------------------------------------------------------------
                                     (Print)

Address:
        ------------------------------------------------------------------------

--------------------------------
          (Signature)

Dated:                                 Signature Guaranteed:
      --------------------------------

                                     NOTICE

         The signature on the foregoing Assignment must correspond to the name
as written upon the face of this Representative's Option in every particular,
without alteration or enlargement or any change whatsoever. Signature(s) must be
guaranteed by an eligible guarantor institution which is a participant in a
Securities Transfer Association recognized program.<PAGE>
                                                                     EXHIBIT 4.6

                          CONSULTING SERVICES AGREEMENT

         This Consulting Agreement dated as of _______________, 2002 is entered
into by and between Natural Gas Services Group, Inc. (the "Company") and
Neidiger, Tucker, Bruner, Inc. (the "Consultant").

         RECITALS

         WHEREAS, the Consultant has experience in the financial consulting
business; and

         WHEREAS, the Consultant desires to provide the financial consulting
services (the "Services") set forth in Section 3 hereof to the Company and the
Company desires to retain the Consultant to provide the Services to the Company.

         NOW THEREFORE, in consideration of the promises and the mutual
covenants and agreements hereinafter set forth, the parties hereto agree as
follows:

         1. Retention. The Company hereby retains the Consultant, and the
Consultant agrees to be retained by the Company, to perform the Services as a
Consultant to the Company on the terms and conditions set forth herein. The
parties agree that the Consultant shall be retained by the Company as an
independent contractor on a consulting basis and not as an employee of the
Company.

         2. Term. The term of this Agreement shall commence on the date hereof
and shall end on _______________, 2005.

         3. Duties of Consultant. During the term of this Agreement, Consultant
shall provide the Company with such regular and customary advice as is
reasonably requested by the Company, within the scope of the Services enumerated
below. It is understood and acknowledged by the parties that the value of
Consultant's advice cannot be readily quantified, and that Consultant shall be
obligated to render advice upon the request of the Company, in good faith, but
not be obligated to spend any specific amount of time so doing. Consultant's
duties shall include, but will not be limited to, providing recommendations
concerning one or more of the following related matters upon the request of the
Board of Directors of the Company and/or its President.

            a. Assisting in the introduction of the Company to registered
         representatives at  various registered broker/dealers;

            b. Arranging, on behalf of the Company, meetings with securities
         analysts of regional investment banking firms;

            c. Rendering financial advice with regard to corporate matters;

            d. Furnishing advice to the Company in connection with prospective
         acquisitions and/or merger candidates;

<PAGE>

            e. Participating as a financial advisor at meetings of the Company's
         Board of Directors or any committee thereof;

            f. Using its best efforts to cause research reports concerning the
         Company to be written and disseminated by investment banking firms; and

            g. Using its best efforts to provide the Company with market-makers
         in its Common Stock, which market-makers have not previously made a
         market in the Company's securities;

         The Company may, at any time, request additional duties and services of
the Consultant. The Consultant will provide the Company a fee structure for such
additional services upon request.

         4. Compensation. In consideration for the Services to be rendered by
the Consultant to the Company pursuant to this Agreement, the Company shall pay
to the Consultant $3,000 on the first day of each month during that month during
the term of this Agreement commencing _______________, 2002.

         5. Expenses. The Company will promptly reimburse Consultant for all
reasonable and required out-of-pocket expenses properly incurred by the
Consultant in performance of this Agreement provided that the Company has
approved such expenses in advance and provided further that a written
accounting, reasonable and acceptable to the Company is made by the Consultant.

         6. Confidentiality. Consultant acknowledges that as a consequence of
its relationship with the Company, it has been and will continue to be given
access to ideas, trade secrets, methods, customer information, business plans
and other confidential and proprietary information of the Company (collectively,
"Confidential Information"). Consultant agrees that it shall maintain in
confidence and shall not disclose directly or indirectly to any third parties
for use for any purposes (other than the performance hereof) the Confidential
Information for the term of this Agreement and a period of two years thereafter,
unless previously approved by the Company in writing. The parties hereto agree
that irreparable damage would occur in the event that any of the provisions of
this Section 6 are not performed by the Consultant in accordance with the
specific terms or are otherwise breached by the Consultant. It is accordingly
agreed that the Company shall be entitled to an injunction or injunctions to
prevent breaches of this Section 6 and to enforce specifically the terms and
provisions hereof in any court of the United States or any State having
jurisdiction in addition to any other remedy to which they are entitled at law
or in equity. Upon termination of the Agreement, the Consultant shall
immediately return all Confidential Information related to the Company under
this Agreement.

         7. Compliance with Law. The Consultant agrees that in performing this
Agreement the Consultant shall comply with the applicable provisions of the
Securities Act of 1933 and the Securities Exchange Act of 1934, as amended, the
applicable rules and regulations of the Securities and Exchange Commission
thereunder, the statutes of any state security commissions

                                       2
<PAGE>

and departments, the applicable rules and regulations of the National
Association of Securities Dealers, Inc. and any other applicable federal, state
or foreign laws, rules and regulations.

         8. Indemnity. The Consultant shall indemnify the Company, its
directors, officers, stockholders, representatives, agents and affiliates
(collectively, the "Affiliated Parties") from and against any and all claims,
losses, damages, fines, fees, penalties, deficiencies, expenses, including
expenses of investigations, court costs and fees and expenses of attorneys which
the Company or its Affiliated Parties may sustain at any time resulting from,
arising out of or relating to the breach or failure to comply with any of the
covenants or agreements of the Consultant or its Affiliated Parties contained in
this Agreement.

         The Company shall indemnify the Consultant, its directors, officers,
stockholders, representatives, agents and affiliates from and against any and
all claims, losses, damages, fines, fees, investigations, court costs and fees
and expenses of attorneys which the Consultant or its affiliated parties may
sustain at any time resulting from, arising out of or relating to the breach or
failure to comply with any of the covenants or agreements of the Company or as a
result of any untrue statement or fact provided by the Company to the Consultant
in the performance of its services under this Agreement.

         9. Applicable Law. This Agreement shall be governed by the internal
laws of the State of Colorado without regard to its conflict of law provisions.

         If the foregoing sets forth your understanding of our Agreement, kindly
indicate your compliance on the space provided below.

AGREED AND ACCEPTED BY:

NATURAL GAS SERVICES GROUP, INC.

By:
   ------------------------------------      -----------------------------------
                                             Date
Its:
    -----------------------------------

NEIDIGER, TUCKER, BRUNER, INC.

By:
   ------------------------------------      -----------------------------------
   Anthony B. Petrelli, Vice President       Date

                                       3

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