Document:

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                                                                    EXHIBIT 4.16

                              ALTRA HOLDINGS, INC.
              INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

NUMBER                                                                    SHARES
AH

COMMON STOCK                                                   SEE REVERSE FOR
                                                             CERTAIN DEFINITIONS

THIS CERTIFIES THAT                                            CUSIP 02208R 10 6

is the owner of

    FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK $.001 PAR VALUE OF

ALTRA HOLDINGS, INC., transferable on the books of the corporation by such owner
in person or by attorney upon surrender of this certificate duly endorsed or
assigned. This certificate and the shares represented hereby are subject to the
laws of the State of Delaware and the Certificate of Incorporation and By-Laws
of the corporation, as now in effect or hereinafter amended. This certificate is
not valid until countersigned and registered by the Transfer Agent and
Registrar.

Dated:

 /s/ David Wall                                        /s/ Carl R. Christenson

                                     (SEAL)

  TREASURER                                                          PRESIDENT

COUNTERSIGNED AND REGISTERED:
  AMERICAN STOCK TRANSFER & TRUST COMPANY
             (NEW YORK, NY)
      TRANSFER AGENT AND REGISTRAR

BY

        AUTHORIZED SIGNATURE

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THE CORPORATION IS AUTHORIZED TO ISSUE MULTIPLE CLASSES AND SERIES OF STOCK. THE
FULL TEXT OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE, PARTICIPATING,
OPTIONAL OR OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OR SERIES THEREOF AND
THE QUALIFICATIONS, LIMITATIONS, OR RESTRICTIONS OF SUCH PREFERENCES AND/OR
RIGHTS, ALL VESTING POWERS, QUALIFICATIONS AND SPECIAL AND RELATIVE RIGHTS OF
THE SHARES OF EACH SUCH CLASS, AS SET FORTH IN THE CERTIFICATE OF INCORPORATION,
WILL BE FURNISHED TO THE HOLDER HEREOF WITHOUT CHARGE, UPON WRITTEN REQUEST TO
THE CORPORATION.

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

TEN COM  - as tenants in common   UNIF GIFT MIN ACT-__________Custodian_________
TEN ENT  - as tenants by the                            (Cust)          (Minor)
           entireties

JT TEN   - as joint tenants with                  under Uniform Gifts to Minors
           right of survivorship
           and not as tenants                        Act________________________
           in common                                           (State)

     Additional abbreviations may also be used though not in the above list.

   For value received,________hereby sells, assigns and transfers unto

   NOTICE: The signature to this assignment must correspond with the name as
written upon the face of the Certificate, in every particular, without
alteration or enlargement, or any change whatever.

  PLEASE INSERT SOCIAL SECURITY OR
OTHER IDENTIFYING NUMBER OF ASSIGNEE

________________________________________________________________________________

________________________________________________________________________________
PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS INCLUDING POSTAL ZIP CODE OF ASSIGNEE

________________________________________________________________________________

________________________________________________________________________________

__________________________________________________________________________Shares

of the common stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint______________________________________________

________________________________________________________________________________
Attorney to transfer the said stock on the books of the within-named corporation
with full power of substitution in the premises.

Dated,___________

                                        ________________________________________

Signature(s) Guaranteed

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

KEEP THIS CERTIFICATE IN A SAFE PLACE. IF IT IS LOST, STOLEN, MUTILATED OR
DESTROYED, THE CORPORATION WILL REQUIRE A BOND OF INDEMNITY AS A CONDITION TO
THE ISSUANCE OF A REPLACEMENT CERTIFICATE.<PAGE>

                                                                    EXHIBIT 4.17

                                SECOND AMENDMENT
                                     TO THE
                  AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

          This Second Amendment to the Amended and Restated Stockholders
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 "Stockholder" and
collectively, the "Stockholders") in order to amend and modify that certain
Amended and Restated Stockholders Agreement, dated as of January 6, 2005 (the
"Agreement"), as amended by the First Amendment to the Amended and Restated
Stockholders Agreement, dated May 1, 2005. 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 Stockholders desire to amend the
Agreement; and

            WHEREAS, Section 15(e) of the Agreement provides that the Agreement
may be amended by the written consent of the Company and Stockholders owning a
majority of the Company's Securities, subject to certain exceptions.

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

      Section 1. Certain Definitions. Section 1(q) of the Agreement shall be
deleted in its entirety and replaced with the following:

      "(q) QUALIFIED PUBLIC OFFERING" means any underwritten initial Public
Offering."

      Section 2. Covenants. Section 7(e) of the Agreement shall be deleted in
its entirety and replaced with the following:

      "(e) Termination. The covenants and agreement set forth in Section 7(a)
shall survive for a period of five (5) years after the date hereof. As to each
Management Stockholder, the covenants and agreement set forth in Section 7(b)
shall survive for a period of one year and one day after such Management
Stockholder ceases to be an employee of the Company, and the covenants and
agreements set forth in Section 7(c) shall survive for a period of two (2) years
plus one day after such Management Stockholder ceases to be an employee of the
Company. The covenants and agreement set forth in Section 7(d) (i) shall
terminate and be of no further force or effect immediately upon consummation of
Altra's or the Company's initial Public Offering, and (ii) (other than Section
7(d)(iii)) shall not be in effect during such time as Altra or the Company is
filing such

                                       1
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information pursuant to the periodic reporting requirements of Sections 12(g) or
15(d) of the Exchange Act."

      Section 3. 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.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       2
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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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS 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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

            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 SECOND AMENDMENT TO
                   AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

<PAGE>

                                   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

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