UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G (Under the Securities Exchange Act of 1934) (Amendment No.)* NATURAL GAS SERVICES GROUP ------------------------------------------------------ (Name of Issuer) COMMON STOCK -------------------------------------- (Title of Class of Securities) 63886Q109 ----------------------- (Cusip Number) December 31, 2004 ______________________________________ (Date of event which requires filing of this statement) Check the appropriate box to designate the rule pursuant to which this schedule is filed: [X] Rule 13d-1 (b) [ ] Rule 13d-1 (c) [ ] Rule 13d-1 (d) *The remainder of this cover page shall be filled out for a reporting person's initial filing of this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act, but shall be subject to all other provisions of the Act (however, see the Notes.) [Continued on the following page(s)] Page 1 of 4 Pages CUSIP No. 63886Q109 2 of 4 Pages ---------------------------------------------------------------- 1. Name of reporting person S.S. or I.R.S. identification no. of above person Babson Capital Management LLC 51-0504477 2. Check the appropriate box if a member of a group (a)( ) (b)( X ) ---------------------------------------------------------------- 3. SEC use only ---------------------------------------------------------------- 4. Citizenship or place of organization Delaware ---------------------------------------------------------------- Number of shares beneficially owned by each reporting person with 5. Sole Voting Power 641,400 ___________________ 6. Shared Voting Power 10,300 __________________________ 7. Sole Dispositive Power 651,700 _______________________________ 8. Shared Dispositive Power 0 --------------------------------------------------------------- 9. Aggregate amount beneficially owned by each reporting person 651,700 --------------------------------------------------------------- 10. Check if the aggregate amount in row (9) excludes certain shares* ---------------------------------------------------------------- 11. Percent of class represented by amount in row 9. 10.74% ---------------------------------------------------------------- 12. Type of Reporting person IA Page 3 of 4 Pages Cusip #: 63886Q109 SCHEDULE 13G ITEM 1(A): NAME OF ISSUER: NATURAL GAS SERVICES GROUP 1(B): ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: 2911 SCR 1260 Midland, TX 79706 ITEM 2(A): NAME OF PERSON FILING: Babson Capital Management LLC (Babson Capital) ITEM 2(B): ADDRESS OF PRINCIPAL BUSINESS OFFICE: One Memorial Drive Cambridge, Massachusetts 02142-1300 ITEM 2(C): CITIZENSHIP: See Item 4 of Cover Page ITEM 2(D): TITLE OF CLASS OF SECURITIES: See Cover Page ITEM 2(E): CUSIP NUMBER: See Cover Page ITEM 3: TYPE OF REPORTING PERSON: If this statement is filed pursuant to Sections 240.13d-1 (b) or 240.13d-2 (b) or (c), check whether the filing person is a: (e) [x] An investment adviser in accordance with Section 240.13d-1 (b) (1) (ii) (E) ITEM 4: OWNERSHIP: (a) AMOUNT BENEFICIALLY OWNED: Babson Capital,in its capacity as investment adviser, may be deemed the beneficial owner of 651,700 shares of common stock of the Issuer which are owned by investment advisory client(s). (b) PERCENT OF CLASS: 10.74% (c) For information on voting and dispositive power with respect to the above listed shares, see Items 5 - 8 of Cover Page. Page 4 of 4 Pages Cusip #:63886Q109 ITEM 5: OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS: N/A ITEM 6: OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON: N/A ITEM 7: IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY: Not Applicable ITEM 8: IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP: Not Applicable ITEM 9: NOTICE OF DISSOLUTION OF GROUP: Not Applicable ITEM 10: CERTIFICATION: By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purpose or effect. SIGNATURE: After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Date: February 8, 2005 Signature: --//Leslie A. Meinhart//-- Name/Title: LESLIE A. MEINHART Compliance Manager February 8, 2005 Securities and Exchange Commission Operations Center Attn: Stop 0-7 6432 General Green Way Alexandria, VA 22312-2413 Re: SCHEDULE 13G RELATING TO COMMON STOCK OF NATURAL GAS SERVICES GROUP FOR THE YEAR ENDING DECEMBER 31, 2004 Dear Sir or Madam: Babson Capital Management LLC is filing today an initial Schedule 13G through the EDGAR system as required by Section 240.13d-1(b) to reflect beneficial ownership of greater than 5% of the outstanding stock of the above-mentioned issuer. Please note that the shares as to which this Schedule is filed are owned by various investment advisory clients of Babson Capital, which may be deemed a beneficial owner of the shares only by virtue of the direct or indirect investment discretion it possesses pursuant to the provisions of investment advisory agreements with such clients. A copy of the Schedule 13G is being sent to the issuer as required by Rule 13d-7. Comments or questions concerning the above may be directed to the undersigned at (617) 761-3798. Sincerely, // Leslie A. Meinhart // LESLIE A. MEINHART Compliance Manager