FOURTH  SUPPLEMENTAL  INDENTURE,  effective as of December 31,
2000, to the  Indenture,  dated as of September 20, 1996, as heretofore  amended
and  supplemented  (the  "Indenture"),  between  Commonwealth  Industries,  Inc.
(formerly  Commonwealth  Aluminum  Corporation),  a  Delaware  corporation  (the
"Company"),  each of the Subsidiary  Guarantors (as defined  therein) and Harris
Trust and Savings Bank, as Trustee (the "Trustee").

                                    RECITALS:

                  The Indenture has heretofore been amended and  supplemented by
a First  Supplemental  Indenture,  dated  as of  November  12,  1996,  a  Second
Supplemental  Indenture,  dated as of October 16, 1998 and a Third  Supplemental
Indenture  dated as of December  31, 1999.  Subsequent  to the date of the Third
Supplemental  Indenture  and  prior to the date  hereof,  the  Company  has duly
organized Alflex Corporation,  a Delaware corporation  ("Alflex"),  Commonwealth
Aluminum Lewisport,  LLC, a Delaware limited liability company ("Lewisport"),and
Commonwealth   Aluminum  Metals,  LLC,  a  Delaware  limited  liability  company
("Metals"),  as  Restricted  Subsidiaries,  and  it  is  proposed  that  Alflex,
Lewisport and Metals become additional  Subsidiary  Guarantors,  as permitted by
Section 901(7) of the Indenture.

                  Also  subsequent  to  the  date  of  the  Third   Supplemental
Indenture  and  prior to the  date  hereof,  the  former  Commonwealth  Aluminum
Lewisport,  Inc.  amended its Certificate of Incorporation to change its name to
CA Lewisport, Inc., and the former Alflex Corporation amended its Certificate of
Incorporation to change its name to CI Holdings,  Inc. and the Company,  each of
the Subsidiary  Guarantors  and Alflex,  Lewisport and Metals have requested the
consent of the Trustee to such name changes.

                  The Company,  each of the  Subsidiary  Guarantors  and Alflex,
Lewisport  and Metals have been  authorized by Board  Resolutions  to enter into
this supplemental indenture.

                  NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE
WITNESSETH:

                  For  and in  consideration  of the  premises,  it is  mutually
agreed,  for  the  equal  and  proportionate  benefit  of  all  Holders  of  the
Securities, as follows:

                                   ARTICLE ONE

                                   Definitions

                  For all purposes of this  supplemental  indenture,  unless the
context otherwise  requires,  the terms used herein shall have the same meanings
as in the Indenture.



                                   ARTICLE TWO

                              Subsidiary Guarantors

                  Alflex,  Lewisport  and  Metals are  hereby  subjected  to the
provisions  (including the  representations  and warranties) of the Indenture as
Subsidiary Guarantors, all as contemplated by Section 1303 of the Indenture.


                                  ARTICLE THREE

                           Consent to Changes of Names

                  The  Trustee,  on behalf  of all  Holders  of the  Securities,
hereby  (i)  consents  to  the  change  in the  name  of  Commonwealth  Aluminum
Lewisport,  Inc. to CA Lewisport,  Inc.,  and (ii) consents to the change in the
name of Alflex Corporation to CI Holdings, Inc.

                  IN WITNESS  WHEREOF,  the  parties  hereto  have  caused  this
Supplemental Indenture to be duly executed, and their respective corporate seals
to be  hereunto  affixed  and  attested,  all as of the day and year first above
written.

                                    COMMONWEALTH INDUSTRIES, INC.
                                    COMMONWEALTH ALUMINUM CORPORATION
                                    COMMONWEALTH ALUMINUM CONCAST, INC.
                                    CA LEWISPORT, INC.
                                    COMMONWEALTH ALUMINUM SALES CORPORATION
                                    CI HOLDINGS, INC.


                                    By:   ______________________________
                                          Mark V. Kaminski
                                          President and Chief Executive Officer



Attest:



By:    ______________________________
       Assistant Secretary




                                    ALFLEX E1 LLC

                                    By:  CI Holdings, Inc.,
                                    as Managing Member



                                    By:   ______________________________
                                          Mark V. Kaminski
                                          President and Chief Executive Officer

Attest:

By:    ______________________________
       Assistant Secretary

                                    ALFLEX CORPORATION


                                    By:   ______________________________
                                          Mark V. Kaminski
                                          President and Chief Executive Officer

Attest:

By:    ______________________________
       Assistant Secretary


                                    COMMONWEALTH ALUMINUM LEWISPORT, LLC


                                    By:   CA Lewisport, Inc.
                                          as Managing Member

                                          By:    ______________________________
                                                 Mark V. Kaminski
                      President and Chief Executive Officer

Attest:

By:    ______________________________
       Assistant Secretary


<PAGE>


                                    COMMONWEALTH ALUMINUM METALS, LLC

                                    By:   Commonwealth Aluminum Lewisport, LLC,
                                          its sole Member

                   By: CA Lewisport, Inc., its Managing Member

                      By: ________________________________
                          Mark V. Kaminski
                          President and Chief Executive Officer

Attest:

By:    ______________________________
       Assistant Secretary



                                    HARRIS TRUST AND SAVINGS BANK,
                                    as Trustee



                                    By:          ______________________________
                                    Name: ______________________________
                                    Title:       ______________________________

Attest:



By:    ______________________________
       Secretary




<PAGE>


COMMONWEALTH OF KENTUCKY            )
                                                 )     ss.:
COUNTY OF JEFFERSON                              )

                  On the _____ day of January,  2001,  before me personally came
Mark V. Kaminski,  to me known,  who, being by me duly sworn, did depose and say
that he is  President  and  Chief  Executive  Officer  of  each of  Commonwealth
Industries,  Inc.,  Commonwealth  Aluminum  Corporation,  Commonwealth  Aluminum
Concast, Inc., CA Lewisport,  Inc.,  Commonwealth Aluminum Sales Corporation and
CI Holdings,  Inc.,  corporations  described in and which executed the foregoing
instrument; that he knows the seal of said corporations;  that the seals affixed
to said  instrument  are such  corporate  seals;  that they were so  affixed  by
authority of the Boards of Directors  of said  corporations,  and that he signed
his name thereto by like authority.

       My Commission expires: ___________________.


                                               ------------------------------
                                                       Notary Public

COMMONWEALTH OF KENTUCKY            )
                                                 (     SS:
COUNTY OF JEFFERSON                              )

       On the ____ day of  January,  2001,  before  me  personally  came Mark V.
Kaminski,  to me known,  who, being by me duly sworn, did depose and say that he
is  President  and  Chief  Executive  Officer  of CI  Holdings,  Inc.,  which is
described in and executed the  foregoing  instrument  as the Managing  Member of
Alflex E1 LLC, a Delaware limited liability  company;  that he knows the seal of
said  corporation,  that the seal affixed to said  instrument is such  corporate
seal;  that it was so affixed by  authority  of the Board of  Directors  of said
corporation and that he signed his name thereto by like authority.

       My Commission expires:  _______________________.


                                           -----------------------------------
                                                       Notary Public



<PAGE>


COMMONWEALTH OF KENTUCKY            )
                                                 )     ss.:
COUNTY OF JEFFERSON                              )

       On the _____ day of  January,  2001,  before me  personally  came Mark V.
Kaminski,  to me known,  who, being by me duly sworn, did depose and say that he
is  President  and Chief  Executive  Officer of CA  Lewisport,  Inc., a Delaware
corporation,  which is described in and executed the foregoing instrument as the
Managing Member of Commonwealth  Aluminum  Lewisport,  Inc., a Delaware  limited
liability  company;  that he knows the seal of said  corporation,  that the seal
affixed to said  instrument is such  corporate  seal;  that it was so affixed by
authority of the Board of Directors of said  corporation  and that he signed his
name thereto by like authority.

       My Commission expires: ___________________.


                                             ---------------------------------
                                                       Notary Public


COMMONWEALTH OF KENTUCKY            )
                                                 )     ss.:
COUNTY OF JEFFERSON                              )

       On the _____ day of  January,  2001,  before me  personally  came Mark V.
Kaminski,  to me known,  who, being by me duly sworn, did depose and say that he
is  President  and Chief  Executive  Officer of CA  Lewisport,  Inc., a Delaware
corporation;  which is described in and executed the foregoing instrument as the
Managing  Member of Commonwealth  Aluminum  Lewisport,  LLC, a Delaware  limited
liability  company,  which is the sole member of Commonwealth  Aluminum  Metals,
LLC,  a  Delaware  limited  liability  company;  that he knows  the seal of said
corporation,  that the seal affixed to said  instrument is such corporate  seal;
that  it was so  affixed  by  authority  of  the  Board  of  Directors  of  said
corporation and that he signed his name thereto by like authority.

       My Commission expires: ___________________.


                                             ---------------------------------
                                                       Notary Public



<PAGE>


STATE OF ILLINOIS )
                                    )     ss.:
COUNTY OF COOK    )

       On the ______ day of  January,  2001,  before me  personally  came Judith
Bartolini,  to me know, who, being by me duly sworn, did depose and say that she
is a Vice  President of Harris Trust and Savings Bank,  one of the  corporations
described in and which  executed the  foregoing  instrument;  that she knows the
seal of said  corporation;  that the seal  affixed  to said  instrument  is such
corporate seal; that it was so affixed by authority of the Board of Directors of
said corporation, and that she signed her name thereto by like authority.

       My Commission expires: _________________.


                                               ------------------------------
                                                       Notary Public




#10139149 v1
12/7/00 3:36 PM