Document:

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                                                                    EXHIBIT 4.18

                                 FIRST AMENDMENT
                                     TO THE
                              AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

            This First Amendment to the Amended and Restated Registration Rights
Agreement (this "Amendment"), dated as of            , 2006, is entered into by
and among Altra Holdings, Inc., a Delaware corporation (the "Company"), and each
of the parties named on Schedule A hereto (each a "Holder" and collectively, the
"Holders") in order to amend and modify that certain Amended and Restated
Registration Rights Agreement, dated as of January 6, 2005 (the "Agreement").
Capitalized terms used but not otherwise defined herein shall have the meanings
ascribed to such terms in the Agreement.

                                    RECITALS:

            WHEREAS, the Company and the Holders desire to amend the Agreement;
and

            WHEREAS, Section 10(b) of the Agreement provides that the Agreement
may be amended by the written consent of the Company and Holders owning at
least 66-2/3% of the Company's Registrable Securities, subject to certain
exceptions.

            NOW, THEREFORE, the parties to this Amendment, intending to be
legally bound hereby, agree as follows:

      Section 1. Definitions. The definition of "Qualified Public Offering" in
Section 1 of the Agreement shall be deleted in its entirety and replaced with
the following:

      ""QUALIFIED PUBLIC OFFERING" means any underwritten initial Public
Offering."

      Section 2. Effectiveness. This Amendment shall become effective as of the
date first above written. Except as otherwise provided in this Amendment, all
terms and conditions of the Agreement shall remain in full force and effect.

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ALTRA HOLDINGS, INC.

                                     By:
                                           _____________________________________
                                             Name:
                                             Title:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     GENSTAR CAPITAL PARTNERS III, L.P.

                                     By:     Genstar Capital III, L.P.
                                     Its:    General Partner

                                             By:    Genstar III GP LLC
                                             Its:   General Partner

                                             By:
                                                  ______________________________
                                                  Name:
                                                  Title:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     STARGEN III, L.P.

                                     By:     Genstar Capital III, L.P.
                                     Its:    General Partner

                                             By:    Genstar III GP LLC
                                             Its:   General Partner

                                             By:
                                                  ______________________________
                                                  Name:
                                                  Title:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     CAISSE DE DEPOT ET PLACEMENT DU QUEBEC

                                           By:
                                               _________________________________
                                               Name:
                                               Title:

                                           By:
                                               _________________________________
                                               Name:
                                               Title:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Michael L. Hurt

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     William J. Duff

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Thomas F. Tatarczuch

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Donald S. Wierbinski

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Craig Schuele

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Gerald Ferris

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Edward L. Novotny

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Mark Stuebe

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Timothy McGowan

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Larry McPherson

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Lee Hess

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Thomas Hunt

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Carl R. Christenson

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Virginia Christenson

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     David A. Wall

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     David Ebling

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

<PAGE>

            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     David Zietlow

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     ___________________________________________
                                     Frank E. Bauchiero

                                     Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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            IN WITNESS WHEREOF, this Amendment has been duly executed and
delivered by the parties as of the date first set forth above.

                                     FRANK BAUCHIERO MKC WORLDWIDE

                                     By:
                                            ____________________________________
                                     Name:
                                     Title:

                                            Address:

                      SIGNATURE PAGE TO FIRST AMENDMENT TO
               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

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                                   SCHEDULE A

                              LIST OF STOCKHOLDERS

Genstar Capital Partners III, L.P.
Stargen III, L.P.
Caisse de depot et placement du Quebec
Michael L. Hurt
William J. Duff
Thomas F. Tatarczuch
Donald S. Wierbinski
Craig Schuele
Gerald Ferris
Edward L. Novotny
Mark Stuebe
Timothy McGowan
Larry McPherson
Lee Hess
Thomas Hunt
Frank Bauchiero MKC Worldwide
Frank E. Bauchiero
Carl R. Christenson
Virginia Christenson
David Wall
David Zietlow
David Ebling<PAGE>
                                                                   EXHIBIT 10.20

                                 FIRST AMENDMENT
                                     TO THE
                           ADVISORY SERVICES AGREEMENT

         THIS FIRST AMENDMENT (this "Amendment") to that certain Advisory
Services Agreement ("Advisory Services Agreement"), dated as of November 30,
2004, among Altra Holdings, Inc. ("Holdings"), Altra Industrial Motion, Inc.
("Altra") and Genstar Capital, L.P. ("Genstar"), is entered into as of November
30, 2006, among Holdings, Altra and Genstar.

                                    RECITALS

         WHEREAS, Holdings has announced its intention to conduct an initial
public offering of its common stock , par value $0.001 per share
(the "Offering");

         WHEREAS, pursuant to the Advisory Services Agreement, Genstar has and
will provide certain management, business strategy, consulting and financial
services to the Company in connection with the Offering (the "Services");

         WHEREAS, the parties hereto desire to amend the terms of the Advisory
Services Agreement to clarify the fees payable to Genstar for its Services in
connection with the Offering;

         WHEREAS, following the Offering and the payment of all amounts due to
Genstar, the parties hereto desire to terminate the Advisory Services Agreement;

         WHEREAS, the parties hereto desire to amend the terms of the Advisory
Services Agreement as provided in this Amendment pursuant to Section 10 of the
Advisory Services Agreement;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements hereinafter contained, the parties hereby agree as
follows:

1.       Definitions. Capitalized terms not otherwise defined in this Amendment
         have the meaning given them in the Advisory Services Agreement.

2.       Amendment of the Agreement. Effective upon the date hereof, the
         Advisory Services Agreement is amended as follows:

         2.1.     Amendment to Section 2(e) of the Advisory Services Agreement.
                  Section 2(e) of the Advisory Services Agreement is hereby
                  amended to insert the following sentence at the end of the
                  first paragraph of Section 2(e):

                  "Notwithstanding the foregoing, a Disposition shall not
                  include the initial public offering of Company's common stock
                  pursuant to a registration statement under the Securities Act
                  which has been declared effective by the Securities and

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                  Exchange Commission (other than a registration statement on
                  Form S-4, Form S-8 or any other similar form) (an "INITIAL
                  PUBLIC OFFERING")."

         2.2.     Amendment to Section 2 of the Advisory Services Agreement.
                  Section 2 of the Advisory Services Agreement is hereby amended
                  to insert the following Section 2(f) immediately after Section
                  2(e):

                  "(f) In the event an Initial Public Offering is consummated,
                  the Company agrees to pay us an advisory fee of $3,000,000
                  (the "IPO ADVISORY FEE") for our services in connection with
                  such Initial Public Offering. The IPO Advisory Fee will be
                  fully earned and shall be payable by the Company to us on the
                  date of the effectiveness of the Initial Public Offering ."

         2.3.     Amendment to Section 3 of the Advisory Services Agreement.
                  Section 3 of the Advisory Services Agreement is hereby amended
                  to insert the following sentence at the end of Section 3:

                  "Notwithstanding the foregoing, this Agreement shall terminate
                  automatically, immediately following the effectiveness of an
                  Initial Public Offering and the payment of all outstanding
                  amounts due to us, including the IPO Advisory Fee."

3.       No Other Amendments. Except as modified by Section 2 above, the
         Advisory Services Agreement shall continue in full force and effect.

4.       Governing Law. This Amendment shall be governed by and construed in
         accordance with the laws of the State of New York,
         without regard to principles of conflicts of law.

                                   * * * * *

                                       2

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         IN WITNESS WHEREOF, the parties hereto, intending to be legally bound
hereby, have caused this Amendment to be executed as of the date first written
above by their respective officers thereunto duly authorized.

                                           GENSTAR CAPITAL, L.P.

                                           By:  Genstar Management LLC
                                           Its: General Partner

                                           By:_________________________________
                                                Name:
                                                Title:

                                           ALTRA HOLDINGS, INC.

                                           By:_________________________________
                                                Name:  Michael L. Hurt
                                                Title: Chief Executive Officer

                                           ALTRA INDUSTRIAL MOTION, INC.

                                           By:_________________________________
                                                Name:  Michael L. Hurt
                                                Title: Chief Executive Officer

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