Document:

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                                                                   EXHIBIT 10.20

                        PRODUCT DISTRIBUTION AGREEMENT

This Product Distribution Agreement (this "Agreement") is entered into as of
March 31, 2001, between Millipore Corporation ("Millipore"), a Massachusetts
corporation with its principal place of business at 80 Ashby Road, Bedford, MA
01730, and Mykrolis Corporation ("Mykrolis"), a Delaware corporation with its
principal place of business at Patriots Park, Bedford, MA 01730.

                                   RECITALS

     1.   Millipore currently owns all of the issued and outstanding common
stock of Mykrolis.

     2.   Millipore and Mykrolis have entered into a Master Separation and
Distribution Agreement as of March 28, 2001 (the "Master Agreement") under
which, among other things, the business of Millipore's Microelectronics Division
is to be taken over by, and the assets and liabilities associated therewith are
to be transferred to and assumed by, Mykrolis at the Separation Date (as defined
in the Master Agreement).

     3.   After the Separation Date, in order to enable Millipore and Mykrolis
to carry on their respective businesses as separate companies, Millipore and
Mykrolis desire to provide for a product distribution arrangement relating to
certain products that have been historically manufactured by Millipore and sold
to customers of both Millipore's Microelectronics Division and one or more of
Millipore's other divisions, but which will become the products of either
Millipore or Mykrolis following the Separation Date.

     4.   The Master Agreement provides for this Agreement to be entered into as
of the Separation Date.

     NOW, THEREFORE, in consideration of the foregoing and the covenants and
agreements set forth below, the parties hereto agree as follows:

1.   Definitions
     -----------

          The following terms shall have the meanings assigned to them below
whenever they are used in this Agreement.  Capitalized terms used in this
Agreement without definition and which are defined in the Master Agreement shall
have the meanings assigned to them in the Master Agreement.  Except where the
context otherwise requires, words imparting the singular shall include the
plural and vice versa, words denoting any gender shall include all genders and
words denoting persons shall include bodies corporate and vice versa.

     "Distributed Products" shall mean the Millipore Products when Millipore is
the Manufacturer and Mykrolis is the Distributor, and shall mean the Mykrolis
Products when Mykrolis is the Manufacturer and Millipore is the Distributor.
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     "Distributor" shall mean a party to this Agreement that orders certain
Products for distribution pursuant to this Agreement and to whom such Products
are sold.

     "Field of Use" of a party shall mean (i) for Millipore, the Millipore Core
Business, and (ii) for Mykrolis, the Mykrolis Core Business.

     "Manufacturer" shall mean a party to this Agreement that manufactures
certain Products and that sells such Products to the other party for
distribution hereunder.

     "Millipore Products" shall mean  (i) all products included as of the date
                                          ---
of this Agreement in the product lines listed in Exhibit A hereto or thereafter
                                                 ------- -
added to such product lines during the Term of this Agreement, and any improved
or updated versions and/or modifications of any of such products, and (ii) those
products that may become Millipore Products pursuant to Section 17 hereof.

     "Mykrolis Products" shall mean all products included as of the date of this
Agreement in the product lines listed in Exhibit B hereto or thereafter added to
                                         ------- -
such product lines during the Term of this Agreement, and any improved or
updated versions and/or modifications of any of such products, and (ii) those
products that may become Mykrolis Products pursuant to Section 17 hereof.

     "Products" shall mean the Millipore Products and the Mykrolis Products.

     "Releases" shall mean any purchase orders or other documents of purchase
that a Distributor may place with a Manufacturer for Distributed Products.

     "Term" or "Term of this Agreement" shall mean the effective period of this
Agreement as set forth in Section 12 hereof.

2.   Appointment of Distributor.  Millipore hereby appoints Mykrolis as the
     ---------------------------
exclusive worldwide distributor in the Mykrolis Core Business of the Millipore
Products for the Term of this Agreement.  Mykrolis hereby appoints Millipore as
the exclusive worldwide distributor in the Millipore Core Business of the
Mykrolis Products for the Term of this Agreement.  Neither Distributor shall
have any rights hereunder to distribute or resell Distributed Products outside
of its Field of Use, and neither Manufacturer shall be restricted in any way
from selling, distributing or marketing its Products in any fields or industries
other than the corresponding Distributor's Field of Use. Neither the
Manufacturer nor its Affiliated Companies will actively market, advertise,
solicit orders or knowingly accept orders of Distributed Products in the
Distributor's Field of Use, during the Term of this Agreement.  Furthermore, the
Manufacturer shall use reasonable efforts to refer to the Distributor any
customer inquiries in the Distributor's Field of Use.

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3.   Prices.  Each Manufacturer shall sell the Distributed Products to the
     -------
Distributor at a percentage discount  of 35% off its U.S. list price for such
Distributed Products.  The initial pricing will be based on the discount from
the U.S. list prices in effect on the Separation Date, and prices shall be
changed annually thereafter, as of the anniversary of the Separation Date, based
on the discount off U.S. list prices in effect on such anniversary date.  Prices
shall be F.O.B. point of shipment by the Manufacturer.

4.   Responsibilities of the Distributor.
     ------------------------------------

     (a)  Each Distributor shall comply with all laws and regulations applicable
          to its distribution of the Distributed Products, including without
          limitation the U.S. Foreign Corrupt Practices Act of 1977 and all U.S.
          export control laws and regulations.

     (b)  Each Distributor shall use its reasonable best efforts to provide
          service to and to perform all necessary repairs on all Distributed
          Products sold by the Distributor in a prompt, professional and proper
          manner.  If the Manufacturer's personnel are needed to provide
          installation, maintenance, or repair service for Distributed Products
          sold by the Distributor, and the Manufacturer agrees to provide any
          such service, the Manufacturer may charge the Distributor a reasonable
          mutually agreed upon fee for such service.  If any such repair or
          replacement is required while the Distributed Products are still under
          the applicable Manufacturer warranty, the Manufacturer will reimburse
          the Distributor for the cost of replacement parts therefor.

5.   Trademarks, Product Labeling and Packaging.
     -------------------------------------------

     (a)  The trademarks of the Manufacturer and of its Affiliated Companies as
          well as all other present or future trademarks of any of them shall be
          conspicuously displayed and used by the Distributor in the sale and
          promotion of the Distributed Products in a manner identical to or
          consistent with the Manufacturer's own practice.  All such trademarks
          shall be and remain the sole property of the Manufacturer and any use
          thereof by the Distributor shall be limited to the Distributed
          Products.  It is expressly agreed that the Distributor's use of the
          Manufacturer's trademarks is with and on the consent of the
          Manufacturer and that the Distributor shall acquire no rights in said
          trademarks because of its use thereof.  The Distributed Products will
          bear the labeling and artwork of the Manufacturer, as affixed thereon
          by the Manufacturer, and the Distributor will not modify such labeling
          or artwork except to add labels stating "Distributed by [fill in name
          of Distributor].  For service call ________."  or a substantially
          equivalent statement, or as may be otherwise expressly authorized in
          writing by the Manufacturer in its sole discretion.

                                       3
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     (b)  The Manufacturer shall package the Distributed Products in packaging
          configurations currently in effect unless otherwise agreed by the
          parties. At a Distributor's request, and with such Distributor's
          assistance, the Manufacturer agrees to use its reasonable best efforts
          to bar code the Distributed Products in a manner reasonably acceptable
          to the Distributor. The Distributor agrees to accept the
          Manufacturer's methodology for designating and displaying lot numbers
          and expiration dates, if any.

6.   Supply of Distributed Products
     ------------------------------

     (a)  Each Manufacturer agrees to sell to the corresponding Distributor,
          from time to time during the Term, Distributed Products, in the
          amounts contained in the Distributor's Releases. Except as set forth
          in Section 7(a) hereof, neither Distributor shall have any minimum or
          maximum purchase requirements for any or all of such Distributed
          Products hereunder, either per order or in the aggregate.

     (b)  Unless otherwise agreed by both parties in writing, this Agreement
          applies to all Releases placed by a Distributor with the corresponding
          Manufacturer during the Term.  The terms and conditions of this
          Agreement shall apply to any Release, whether or not this Agreement or
          its terms and conditions are expressly referenced in the Release.

     (c)  Unless otherwise agreed by both parties in writing for a specific
          transaction, no inconsistent or additional term or condition in any
          Release, or in any acknowledgment, invoice or other document issued by
          a Manufacturer in connection with a particular purchase by a
          Distributor, shall be applicable to a transaction within the scope of
          this Agreement.  Both parties specifically agree that any terms and
          conditions in any such documents which are in any way inconsistent
          with this Agreement shall be inapplicable, and the terms of this
          Agreement shall govern.

7.   Orders, Delivery and Payment
     ----------------------------

     (a)  Each Distributor will provide the corresponding Manufacturer with a
          rolling one year forecast of its demand for Distributed Products
          hereunder (a "One-Year Forecast") which will be updated on a quarterly
          basis, at least thirty (30) days prior to the start of each calendar
          quarter.  Each such One-Year Forecast shall include a sub-forecast for
          the first three months within the One-Year Forecast (a "3 Month
          Forecast") The Distributor must provide Releases for delivery, during
          the three months covered by such 3 Month Forecast, of such Distributed
          Products in quantities not more than 25% less or 25% greater than the
          quantities set forth in such 3 Month Forecast.  Except for such semi-
          binding nature of the 3 Month Forecasts, the One-Year Forecasts will
          be used for planning purposes only and are not binding.  A
          Manufacturer will ship

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          Distributed Products so as to arrive on the delivery date set forth in
          a Release, provided that the delivery date set forth in such Release
          is not less than 30 days following the date such Manufacturer receives
          such Release and provided that the amounts set forth in such Release
          are within the range provided above in accordance with the applicable
          3 Month Forecast.

     (b)  A Distributor shall make payment to the Manufacturer within forty-five
          (45) days after the later of (i) receipt of ordered Distributed
          Products, and (ii) receipt of such Manufacturer invoice for such
          Distributed Products.  All payments shall be made in U.S. Dollars.
          Late payments shall be subject to interest at a rate of 12% per annum.

     (c)  All Distributed Products shall be tested, inspected and packaged for
          delivery by the Manufacturer in accordance with its standard
          procedures.

     (d)  All Distributed Products shall be delivered to the Distributor or its
          designated Affiliated Company in the country of manufacture of such
          Distributed Products or, if there is no Affiliated Company of the
          Distributor in such country of manufacture, then to a mutually
          agreeable Distributor or Affiliated Company location.  A Manufacturer
          shall not be required to drop-ship any Distributed Products to any
          customer or to any other Affiliated Company of the Distributor.

8.   Ownership of Goodwill; Waiver of Indemnity.  Each Distributor agrees that
     -------------------------------------------
the discounts provided in Section 3 hereof shall constitute full and adequate
compensation for the performance of its obligations hereunder and that any
enhancement of the Manufacturer's goodwill arising out of the sale of the
Distributed Products or the performance by the Distributor of its obligations
hereunder shall be for the sole and exclusive benefit and account of the
Manufacturer. The Distributor agrees and acknowledges that no franchise
relationship is established hereby. All payments to be made to the Manufacturer
hereunder shall be made in connection with bona fide wholesale transactions with
respect to the Distributed Products. The Distributor hereby waives any rights it
may have under law or otherwise to claim or to receive any indemnity or other
compensation upon termination of this Agreement for whatever cause.

9.   Distributor Not Agent or Legal Representative of Manufacturer.  This
     --------------------------------------------------------------
Agreement does not constitute the Distributor as the agent or legal
representative of the Manufacturer for any purpose whatsoever.  The Distributor
is not granted any right or authority to assume, create or incur any debt,
obligation or responsibility, express or implied, on behalf of or in the name of
the Manufacturer or to bind it in any manner whatsoever.  Nothing herein shall
be deemed to constitute the Manufacturer and the Distributor as partners, joint
venturers or to be otherwise associated with the business of the other; it is
expressly recognized that no fiduciary relationship exists between the parties.

10.  Distributor to Indemnify Manufacturer.  Each Distributor agrees to
     --------------------------------------
indemnify and hold harmless the corresponding Manufacturer and its Affiliated
Companies from all losses

                                       5
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and damages (including attorney's fees) that it or they may sustain or become
liable for by reason of claims against it or them resulting from unauthorized
acts or statements of the Distributor or its employees, agents or
representatives. The Distributor further agrees to indemnify the Manufacturer
and its Affiliated Companies from any claims asserted by the Distributor's
employees or agents for compensation, severance payments, disability or social
service payments.

11.  Subagents.
     ----------

     Each Distributor may use any of its Affiliated Companies or third parties
as subdistributors, agents or commissionaires in the distribution of Distributed
Products hereunder, provided that the Distributor requires any such
subdistributor, agent or commissionaire to be bound by the restrictions
hereunder as to Field of Use, and provided further that the Distributor shall
promptly notify the Manufacturer as to the identity and sales territory of any
such third party distributor, agent or commissionaire.

12.  Term and Termination
     --------------------

     (a)  The effective period of this Agreement (the "Term") shall begin on the
          Separation Date and continue thereafter for a period of five (5) years
          or until earlier termination in accordance with clause (b) of this
          Section 12. Any Release issued by Distributor before the effective
          date of termination and in accordance with Sections 6 and 7 hereof
          shall be fulfilled by the Manufacturer.

     (b)  Either party may (i) terminate this Agreement, or (ii) terminate its
          obligations as Manufacturer and the other party's rights as
          Distributor of such Manufacturer terminating party's Products
          hereunder, prior to the date five (5) years following the Separation
          Date without prejudice to any rights or liabilities accruing up to the
          date of termination:

          (i)  in the event of a material breach by the other party of any of
               the terms and conditions of this Agreement, by giving the other
               party notice of such breach, and provided that such breach shall
               not have been cured within sixty (60) days following such notice;
               and

          (ii) immediately, by written notice thereof, if any of the following
               events or an event analogous thereto occurs:

               a.   an adjudication has been made that the other party is
                    bankrupt or insolvent;

                                       6
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               b.   the other party has filed bankruptcy proceedings or has had
                    such proceedings filed against it, except as part of a bona
                    fide scheme for reorganization;

               c.   a receiver has been appointed for all or substantially all
                    of the property of the other party;

               d.   the other party has assigned or attempted to assign this
                    Agreement for the benefit of its creditors; or

               e.   the other party has begun any proceeding for the liquidation
                    or winding up of its business affairs.

     (c)  A Distributor may terminate its rights and the corresponding
          Manufacturer's obligations under this Agreement with respect to the
          Distributed Products that such Distributor has distributed, effective
          at any time, provided it has given the Manufacturer at least sixty
          (60) days prior written notice thereof.  Any such termination under
          this clause (c) shall not relieve such Distributor of its supply
          obligations or deprive the other party of its distribution rights
          hereunder.

     (d)  Termination under this Section 12 shall be in addition to and not a
          substitute for other rights or causes of action of the terminating
          party.

     (e)  Termination of this Agreement or of a Distributor's rights and the
          corresponding Manufacturer's obligations hereunder shall not in any
          way operate so as to impair or destroy any of the rights or remedies
          of either party, either at law or in equity, nor shall it relieve the
          parties of their obligations pursuant to Sections 4 (a), 5, 8, 9, 10,
          11, 13, 14, 15, 19 and 20 hereof.

     (f)  Each party acknowledges, both in its capacity as a Distributor and as
          a Manufacturer, that it has no right to renew or extend this
          Agreement, or either distribution relationship hereunder, following
          the end of the Term of this Agreement.  This Agreement may be renewed
          or extended only upon and in accordance with the terms of a written
          agreement by the parties to that effect, which the parties are under
          no obligation to negotiate or enter into.

13.  Right to Repurchase of Inventory.  If this Agreement is terminated by
     ---------------------------------
either party for any reason, or if a Distributor's rights and the corresponding
Manufacturer's obligations hereunder are terminated, the Manufacturer may, at
its option, repurchase from the Distributor any or all of the Distributed
Products in the possession of Distributor; provided, that the Manufacturer shall
                                           --------
be under no obligation to exercise this repurchase option.  The repurchase price
for any such inventory which the Manufacturer elects to repurchase shall be the
price paid therefor by the Distributor (including transport and insurance
costs).  The Manufacturer, however, reserves the right to reject any Distributed
Product tendered by the Distributor which

                                       7
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is not in first class condition, which is obsolete or which is otherwise not fit
for resale. Any Distributed Product sold by the Distributor prior to such
termination but not yet installed (assuming installation is necessary) shall be
installed by the Manufacturer and all mutually agreed upon expenses shall be
charged to the Distributor's account and deducted at time of final statement. If
the Manufacturer does not exercise its repurchase option as described above, the
Distributor shall be free to continue to distribute any Distributed Products in
its inventory for a reasonable period of time following such termination, but
not to exceed 18 months, any such distribution to be subject to the applicable
terms hereof.

14.  Warranties, Indemnification and Insurance
     ------------------------------------------

     (a)  Each Manufacturer warrants to the corresponding Distributor that:

          (i)    All Distributed Products supplied to the Distributor hereunder
                 shall conform to the specifications referred to for such
                 Distributed Products in the Manufacturer's published
                 literature;

          (ii)   All Distributed Products shall be free of defects in materials
                 and workmanship;

          (iii)  It will abide by all applicable laws and regulations in
                 manufacturing the Distributed Products; and

          (iv)   All Distributed Products supplied hereunder will be
                 manufactured in strict conformity with ISO 9002 and cGMP
                 standards.

     (b)  In the event of a breach of the foregoing warranties, the
          Manufacturer's sole obligation to the Distributor or any end user
          shall be to repair, replace, or refund, at the Manufacturer's option,
          any non-conforming Distributed Product.

     (c)  THE MANUFACTURER MAKES NO OTHER WARRANTY, EXPRESSED OR IMPLIED,
          INCLUDING WITHOUT LIMITATION ANY WARRANTY OF MERCHANTABILITY OR
          FITNESS FOR A PARTICULAR USE. FURTHERMORE, THE MANUFACTURER SHALL NOT
          BE LIABLE FOR CONSEQUENTIAL, INCIDENTAL, SPECIAL OR ANY OTHER INDIRECT
          DAMAGES RESULTING FROM ECONOMIC LOSS OR PROPERTY DAMAGE SUSTAINED BY
          THE DISTRIBUTOR FROM THE USE OF THE SUPPLIED MEMBRANES.

     (d)  Each Manufacturer agrees to indemnify and hold the corresponding
          Distributor harmless from and against any claim or legal action by a
          third party against such Distributor (including reasonable attorneys'
          fees associated therewith) based on damages incurred as a result of
          property damages, personal injury or death, to the proportionate
          extent arising from a breach of any of the above

                                       8
<PAGE>

          warranties of the Manufacturer or from the Manufacturer's negligent
          action or omission.

     (e)  Without limiting any other rights or remedies that a Distributor may
          have, if such Distributor determines that delivered Distributed
          Products do not conform to the agreed specifications for such
          Distributed Products, then such Distributor may reject or withdraw its
          acceptance thereof and shall notify Manufacturer in writing of such
          nonconformity or error within thirty (30) days from receipt of such
          Distributed Products by the Distributor.  The Manufacturer shall have
          fifteen (15) days after receipt of written notice of nonconformity or
          error to replace nonconforming Distributed Products at the expense of
          the Manufacturer.  If so directed by the Manufacturer, the Distributor
          shall return nonconforming Distributed Products to the Manufacturer's
          manufacturing facility, at the Manufacturer's expense and using such
          carrier and such delivery dates and terms as the Manufacturer shall
          reasonably specify.

     (f)  In the event of a Distributed Product failure confirmed by the
          Manufacturer, or a recall required by a government agency or requested
          by the Manufacturer, the Manufacturer agrees to pay the costs of any
          recall mailing it makes as well as return freight costs.  The
          Manufacturer will also bear the costs of supplying replacement
          products.  All other costs will be for the account of the Distributor.
          In addition, the Manufacturer shall notify the Distributor immediately
          in writing should the Manufacturer become aware of any defect or
          condition which may render any of the Distributed Products in
          violation of any statute or regulation, or which in any way alters the
          specifications or quality of the Distributed Products.

     (g)  Each Manufacturer agrees to procure and maintain, at all times during
          the Term, product liability insurance with respect to the Distributed
          Products supplied by it (Broad Form Vendor's Endorsement) and
          contractual liability coverage, with the minimum limits of $5,000,000
          (Five Million Dollars).  Each Manufacturer shall, upon request by the
          Distributor, furnish to the Distributor a certificate of insurance
          evidencing the foregoing coverage and limits.  The insurance provider
          shall not be changed without providing the Distributor with ten (10)
          days' prior written notice.

15.  Notices
     -------

Any notice or other communication required or permitted to be given by either
party pursuant to the terms of this Agreement shall be in writing and shall be
deemed given if and when delivered by hand or sent by certified mail, return
receipt requested, overnight courier, confirmed telecopy, or confirmed
electronic mail transmission, addressed as follows:

                                       9
<PAGE>

          If to Millipore:         Millipore Corporation
                                   80 Ashby Road
                                   Bedford, MA  01730
                                   Attn: Vice President, Manufacturing
                                   Fax: (781) 533-3120

          with a copy to:          Millipore Corporation
                                   80 Ashby Road
                                   Bedford, MA 01730
                                   Attn: General Counsel
                                   Fax: (781) 533-3125

          If to Mykrolis:          Mykrolis Corporation
                                   Patriots Park
                                   Bedford, MA 01730
                                   Vice President, Manufacturing
                                   Fax: (781) 533-3117

          with a copy to:          Mykrolis Corporation
                                   Patriots Park
                                   Bedford, MA 01730
                                   Attn:  General Counsel
                                   Fax:  (781) 533-3125

or to such electronic mail address as may be specified by an addressee party to
the other party by one of the other means provided above, or to such other
address, telecopy number or electronic mail address as may be specified by an
addressee party to the other by one of the means provided above.

16.  Force Majeure
     -------------

The obligations of a party under this Agreement will be suspended to the extent
that it is wholly or partially precluded from complying with its obligations
under this Agreement by force majeure. Force majeure includes, but is not
restricted to, fire, storm, flood, earthquake, explosion, accident, act of the
public enemy, war, rebellion, insurrection, sabotage, epidemic, quarantine
restriction, labor dispute, labor shortage, transportation embargo or failure or
delay in transportation, act of God, act (including laws, regulations,
disapprovals or failure to approve) of any government agency, whether national,
municipal, or otherwise. During the existence of any such force majeure
condition,the affected party shall nevertheless use its best efforts to remove
the cause thereof.

                                      10
<PAGE>

17.  Additional Products
     -------------------

It is the intention that all products of either Manufacturer that have been sold
into the Distributor's Field of Use during the two (2) year period immediately
preceding the date of this Agreement will be included as Distributed Products of
the Manufacturer hereunder.  If either party discovers any such product that is
not included on Exhibit A or B hereto, as the case may be, such product shall be
                ------- -    -
deemed added to such Exhibit, and considered a Distributed Product of the
Manufacturer, at the request of the Distributor of such product.

18.  Conflicts with Other Agreements
     -------------------------------

In the event that there are any conflicts between the terms of this Agreement
and any distribution agreements of either party or their Affiliated Companies in
effect as of the date hereof, the parties will cooperate with one another in
good faith to attempt to eliminate such conflicts.

19.  Incorporation of Provisions from Master Agreement
     -------------------------------------------------

The following provisions of the Master Agreement, mutatis mutandis, are hereby
                                                  ------- --------
incorporated by reference into this Agreement for all purposes:

          Article VI (Confidentiality);
          Article IX (Dispute Resolution);
          Section 10.3 (Governing Law);
          Section 10.6 (Counterparts);
          Section 10.7 (Binding Effect; Assignment);
          Section 10.8 (Severability);
          Section 10.9 (Failure or Indulgence Not Waiver;
                          Remedies Cumulative);
          Section 10.10 (Amendment);
          Section 10.11 (Authority);
          Section 10.12 (Interpretation).

In the event of any conflict between any of the foregoing incorporated
provisions of the Master Agreement and any other provision of this Agreement,
such other provisions shall prevail.

20.  Entire Agreement
     ----------------

This Agreement, including Exhibits A and B attached hereto, is the entire
                          -------- -------
agreement between the parties with respect to the subject matter hereof, and
supersedes any prior negotiations and agreements or understandings and any
contemporaneous oral agreements or understandings with respect to the subject
matter hereof.

                                      11
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their duly authorized representatives effective as of the date first
set forth above.

MILLIPORE CORPORATION                MYKROLIS CORPORATION

By: /s/ Francis J. Lunger            By:  /s/ Jean Marc Pandraud
   -----------------------               ----------------------------

Name: Francis J. Lunger              Name: Jean Marc Pandraud
     ---------------------                -------------------------

Title: Executive Vice President     Title: President
      --------------------------           -----------------------

                                      12
<PAGE>

                                   EXHIBIT A
                                   ---------

                               Millipore Products
                               ------------------

                  G1  Process Discs
                  H1  Pre/Depth Filter Cartridges
                  H2  Cartridge Products
                  H3  Clarification Cartridges
                  I1  Stacked Disk Products
                  J1  Durapore Cartridges
                  J2  PTFE Cartridges
                  J5  MiE Durapore Filters
                  J6  PES Cartridges
                  M5  Ultra Stak
                  N1  4 Inch Capsule

                                      13
<PAGE>

                                   EXHIBIT B
                                   ---------

                               Mykrolis Products
                               -----------------

                  H4     MiE Chemical Filter Products
                  H5     MiE Photoresist Filters
                  I2     MiE Gas Filter Products
                  M6     Fine Process Products

                                      14<PAGE>

                                                                   Exhibit 10.21

                       CONTRACT MANUFACTURING AGREEMENT

     This Contract Manufacturing Agreement (this "Agreement") is entered into as
of March 31, 2001, between Millipore Corporation ("Millipore"), a Massachusetts
corporation with its principal place of business at 80 Ashby Road, Bedford, MA
01730, and Mykrolis Corporation ("Mykrolis"), a Delaware corporation with its
principal place of business at Patriots Park, Bedford, MA 01730.

                                   RECITALS

     1.   Millipore currently owns all of the issued and outstanding common
stock of Mykrolis.

     2.   Millipore and Mykrolis have entered into a Master Separation and
Distribution Agreement as of March 28, 2001 (the "Master Agreement") under
which, among other things, the business of Millipore's Microelectronics Division
is to be taken over by, and the assets and liabilities associated therewith are
to be transferred to and assumed by, Mykrolis at the Separation Date (as defined
in the Master Agreement).

     3.   After the Separation Date, in order to enable Mykrolis to carry on its
respective business as a separate company, Mykrolis wishes that Millipore, on a
contract manufacturing basis, supply the product (or products) listed on Exhibit
A (the "Product") to Mykrolis, and Millipore wishes to do so.

     4.   The Master Agreement provides for this Agreement to be entered into as
of the Separation Date.

     NOW, THEREFORE, in consideration of the foregoing and the covenants and
agreements set forth below, the parties hereto agree as follows:

1.   Definitions.  Capitalized terms defined in this Agreement shall have the
     -----------
respective meanings assigned to them at the location of their definition.
Capitalized Terms used in this Agreement without definition which are defined in
the Master Agreement shall have the meaning ascribed thereto in the Master
Agreement.

2.   Overriding Character of this Agreement
     --------------------------------------

     A.   Unless otherwise agreed by both parties in writing, this Agreement
          applies to all purchase releases, purchase orders and other documents
          of purchase for the Products (hereinafter collectively referred to as
          "Releases") which Mykrolis may place with Millipore during the term of
          this Agreement.  The terms and conditions of this Agreement shall
          apply to any Releases, whether or not this Agreement or its terms and
          conditions are expressly referenced in the Release.
<PAGE>

     B.   Unless otherwise agreed by both parties in writing for a specific
          transaction, no inconsistent or additional term or condition in any
          Release shall be applicable to a transaction within the scope of this
          Agreement.  Both parties specifically agree that any term and
          condition on any of their purchase or sale documents used as Releases
          hereunder which are in any way inconsistent with this Agreement shall
          be inapplicable, and the terms of this Agreement shall govern.

3.   Supply of Product
     -----------------

     (a)  Millipore agrees to sell to Mykrolis, from time to time during the
          Term, Product, in the amounts contained in Mykrolis's Releases.
          Except as set forth in Section 6(a) hereof, Mykrolis shall have no
          minimum or maximum purchase requirements for the Products.

     (b)  Millipore agrees to manufacture and package the Products in accordance
          with the specifications therefor in effect as of the Separation Date.
          In addition, Millipore agrees to label and otherwise mark the Products
          and the packaging for the Products with Mykrolis's trademarks and
          trade names in accordance with artwork specified by Mykrolis.  Except
          as otherwise expressly agreed, Mykrolis agrees that it shall not
          resell the Products under  any Millipore trademark or trade name.

4.   Term and Termination
     --------------------

     (a)  The effective period of this Agreement (the "Term") shall begin on the
          Separation Date and continue thereafter for a period of five (5) years
          or until earlier termination in accordance with clause (b) or (c) of
          this Section 4. Any Release issued by Mykrolis before the effective
          date of termination and in accordance with Section 6(a) hereof shall
          be fulfilled by Millipore.

     (b)  Either party may terminate this Agreement prior to the expiration of
          the Term without prejudice to any rights or liabilities accruing up to
          the date of termination:

          (i)  in the event of a material breach by the other party of any of
               the terms and conditions of this Agreement, by giving the other
               party notice of such breach, and provided that such breach shall
               not have been cured, or material steps to effect a cure
               undertaken within sixty (60) days following such notice; and

          (ii) immediately, by written notice thereof, if any of the following
               events or an event analogous thereto occurs:

               a.   an adjudication has been made that the other party is
                    bankrupt or insolvent;

                                       2
<PAGE>

               b.   the other party has filed bankruptcy proceedings or has had
                    such proceedings filed against it, except as part of a bona
                    fide scheme for reorganization;

               c.   a receiver has been appointed for all or substantially all
                    of the property of the other party;

               d.   the other party has assigned or attempted to assign this
                    Agreement for the benefit of its creditors; or

               e.   the other party has begun any proceeding for the liquidation
                    or winding up of its business affairs.

     (c)  Mykrolis may terminate this Agreement effective at any time, provided
          it has given Millipore at least sixty (60) days prior written notice
          thereof.

     (d)  Termination under this Section 4 shall be in addition to and not a
          substitute for other rights or causes of action of the terminating
          party.

5.   Price
     -----

     (a)  For the first year of this Agreement, the price shall be as set forth
          on Exhibit A, which is attached and incorporated by reference.
          Thereafter, Millipore shall be entitled to adjust prices annually on
          each anniversary of the Separation Date in order to recoup actual
          increases in the cost to manufacture the Products.  Millipore agrees
          to justify any price increases hereunder by an open-book review of its
          costs with Mykrolis.

     (b)  Prices and deliveries will be FOB the Millipore plant which is
          producing the Product.

6.   Orders, Delivery and Payment
     ----------------------------

     (a)  Mykrolis will provide Millipore with a rolling one year forecast of
          its demand for Product hereunder (a "One-Year Forecast") which will be
          updated on a quarterly basis, at least thirty (30) days prior to the
          start of each calendar quarter. Each such One-Year Forecast shall
          include a sub-forecast for the first three months within the One-Year
          Forecast (a "3 Month Forecast"). Mykrolis shall provide Releases for
          delivery, during the three months covered by such 3 Month Forecast, in
          the quantities specified therein, but subject to increase or reduction
          in such quantities of not more than 25%. Except for such purchase
          commitment in the 3 Month Forecasts, the One-Year Forecasts will be
          used for planning purposes only and are not binding. Millipore will
          ship Product so as to arrive on the delivery date set forth in a
          Release, provided that the delivery date

                                       3
<PAGE>

          set forth in such Release is not less than 30 days following the date
          Millipore receives such Release and provided that the amounts set
          forth in such Release are within the range provided above in
          accordance with the applicable 3 Month Forecast.

     (b)  Mykrolis shall make payment to Millipore within forty-five (45) days
          after the later of (i) receipt of the Product, and (ii) receipt of
          Millipore's invoice for the Product. All payments shall be made in
          U.S. Dollars. Late payments shall bear interest at a rate of 12% per
          annum.

     (c)  All Product shall be tested, inspected and packaged for delivery by
          Millipore as mutually agreed by the parties.

     (d)  Millipore shall make reasonable best efforts to ship the Product in
          accordance with the requested delivery dates.  Millipore shall give
          prompt notice of any delay in shipment and shall use diligence to
          remove the cause of any such delay, provided, however, that Millipore
                                              --------  -------
          accepts no liability for general, special, or consequential damages
          arising out of delay in delivery.

     (e)  Identification of the Products to this Agreement shall occur when they
          are packed for shipment, addressed to Mykrolis and delivered to a
          common carrier, at which time title and risk of loss shall pass to
          Mykrolis.  In the event that any shipment of Products or any portion
          thereof fails to conform to the applicable specifications, then
          Mykrolis shall be entitled to reject such shipment of Products or the
          portion thereof that fails to so conform, as the case may be.
          Mykrolis shall communicate its rejection hereunder by written notice,
          given within twenty (20) days following the date on which such
          shipment was received by Mykrolis, specifying the grounds for such
          rejection.  If no written notice of rejection is given by Mykrolis
          within said twenty (20) day period, the Products shall be deemed to
          have been accepted, and to have conformed to the applicable
          specifications.  In the event of any proper and timely rejection,
          Millipore agrees:  (i) that it shall bear the cost of shipment for the
          return of rejected Products and (ii) to use its reasonable best
          efforts to cure such rejection or replace such nonconforming Products
          within thirty (30) days after receipt of written notice thereof.

7.   Special Covenants.
     ------------------

     (a)  Millipore agrees that the Products are exclusively Mykrolis Products
          and that Millipore agrees that neither it nor any of its Subsidiaries
          shall manufacture, market or sell the Products to any person other
          than Mykrolis or its Subsidiaries.  Notwithstanding the above, if any
          Product is covered by the Product Distribution Agreement entered into
          by Millipore and Mykrolis

                                       4
<PAGE>

          pursuant to the Master Agreement, then Millipore may distribute that
          Product as per the terms of such Product Distribution Agreement.

     (b)  Mykrolis agrees that neither it nor any of its subsidiaries will (i)
          sell the Product into the Millipore Core Business, or (ii) grant any
          distributor, OEM manufacturer or other third party the right or permit
          any of them to sell the Products into the Millipore Core Business

8.   Warranties
     ----------

     Millipore Corporation ("Millipore") warrants the Products will be free
     from defects in materials and workmanship when used in accordance with the
     applicable instructions for a period of one year from shipment of the
     Products.  MILLIPORE MAKES NO OTHER WARRANTY, EXPRESSED OR IMPLIED.  THERE
     IS NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  The
     warranty provided herein and the data, specifications and descriptions of
     Millipore products appearing in Millipore's published catalogues and
     product literature may not be altered except by express written agreement
     signed by an officer of Millipore.  Representations, oral or written, which
     are inconsistent with this warranty or such publications are not authorized
     and if given, should not be relied upon.

     In the event of a breach of the foregoing warranty, Millipore's sole
     obligation shall be to repair or replace, at its option, the applicable
     Product or part thereof, provided Mykrolis notifies Millipore promptly of
     any such breach.  If after exercising reasonable efforts, Millipore is
     unable to repair or replace the Product or part, then Millipore shall
     refund to Mykrolis all monies paid for such applicable product or part.
     MILLIPORE SHALL NOT BE LIABLE FOR CONSEQUENTIAL, INCIDENTAL, SPECIAL OR ANY
     OTHER INDIRECT DAMAGES RESULTING FROM ECONOMIC LOSS OR PROPERTY DAMAGE
     SUSTAINED BY ANY CUSTOMER FROM THE USE OF ITS PRODUCTS.

9.   Product Modifications
     ---------------------

     Millipore agrees that it will not materially change the Product that it
     will supply hereunder or their formulation, manufacturing or testing
     processes, process equipment, other aspects of form, fit or function, or
     production location, unless Mykrolis approves such change in writing, which
     approval may require formal validation and qualification and possibly
     customer notification.  The implementation of any such accepted changes
     shall be subject to the parties' agreement on any change in price or other
     terms of supply as may be necessitated or requested by a party as a result
     of such change.

                                       5
<PAGE>

10.  Inventory
     ---------

     Millipore will maintain an inventory of Product, in such amounts as shall
     be agreed by the parties but in no event less than amounts specified in
     Mykrolis's current 3 Month Forecast.

11.  Access to Facilities
     --------------------

     At any time during the Term, upon reasonable advance notice by Mykrolis,
     Mykrolis's authorized representatives and customers (subject to appropriate
     confidentiality obligations) shall be provided access to the facilities of
     Millipore to audit or verify conformity of Product manufacture to
     specifications.

12.  Notices
     -------

     Any notice or other communication required or permitted to be given by
     either party pursuant to the terms of this Agreement shall be in writing
     and shall be deemed given if and when delivered by hand or sent by
     certified mail, return receipt requested, overnight courier, confirmed
     telecopy, or confirmed electronic mail transmission, addressed as follows:

          If to Millipore:         Millipore Corporation
                                   80 Ashby Road
                                   Bedford, MA  01730
                                   Attn:Vice President, Manufacturing
                                        -----------------------------
                                   Fax: [(781)__________]

          with a copy to:          Millipore Corporation
                                   80 Ashby Road
                                   Bedford, MA 01730
                                   Attn:  General Counsel
                                   Fax:  (781) 533-3125

          If to Mykrolis:          Mykrolis Corporation
                                   Patriots Park
                                   Bedford, MA  01730
                                   Attn:Vice President, Manufacturing
                                        -----------------------------
                                   Fax:  [(781) ________]

          with a copy to:          Mykrolis Corporation
                                   Patriots Park
                                   Bedford, MA  01730

                                       6
<PAGE>

                                   Attn:  General Counsel
                                   Fax:  (781) _________

     or to such electronic mail address as may be specified by an addressee
     party to the other party by one of the other means provided above, or to
     such other address, telecopy number or electronic mail address as may be
     specified by an addressee party to the other by one of the means provided
     above.

13.  Force Majeure
     -------------

     The obligations of a party under this Agreement will be suspended to the
     extent that it is wholly or partially precluded from complying with its
     obligations under this Agreement by force majeure.  Force majeure includes,
     but is not restricted to, fire, storm, flood, earthquake, explosion,
     accident, act of the public enemy, war, rebellion, insurrection, sabotage,
     epidemic, quarantine restriction, labor dispute, labor shortage,
     transportation embargo or failure or delay in transportation, act of God,
     act (including laws, regulations, disapprovals or failure to approve) of
     any government agency, whether national, municipal, or otherwise. The
     parties shall be relieved of their respective obligations hereunder, to the
     extent that the performance of such obligation was actually prevented
     thereby.  During the existence of any such condition, the affected party
     shall, nevertheless, use its best efforts to remove the cause thereof.

14.  No Other Rights
     ---------------

     Neither party shall have any rights hereunder to any patents or other
     intellectual property of the other party, except as specifically set forth
     herein.

15.  Incorporation of Provisions from Master Agreement
     -------------------------------------------------

     The following provisions of the Master Agreement, mutatis mutandis, are
                                                       ------- --------
     hereby incorporated by reference into this Agreement for all purposes:

          Article VI (Confidentiality);
          Article IX (Dispute Resolution);
          Section 10.3 (Governing Law);
          Section 10.6 (Counterparts);
          Section 10.7 (Binding Effect; Assignment);
          Section 10.8 (Severability);
          Section 10.9 (Failure or Indulgence Not Waiver;
                           Remedies Cumulative);
          Section 10.10 (Amendment);
          Section 10.11 (Authority);
          Section 10.12 (Interpretation).

                                       7
<PAGE>

     In the event of any conflict between any of the foregoing incorporated
     provisions of the Master Agreement and any other provision of this
     Agreement, such other provisions shall prevail.

16.  Entire Agreement
     ----------------

     This Agreement, including Exhibit A attached hereto, is the entire
                               ------- -
     agreement between the parties with respect to the subject matter hereof,
     and supersedes any prior negotiations and agreements or understandings and
     any contemporaneous oral agreements or understandings with respect to the
     subject matter hereof.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their duly authorized representatives effective as of the date first
set forth above.

MILLIPORE CORPORATION              MYKROLIS CORPORATION

By: /s/ Francis J. Lunger          By: /s/ Jean-Marc Pandraud
   -----------------------------       ------------------------
Name: Francis J. Lunger            Name: Jean-Marc Pandraud
      --------------------------         ----------------------
Title: Executive Vice President    Title: President
       -------------------------          ---------------------

                                       8
<PAGE>

                        EXHIBIT A:  Product and Prices

Products:      .  Fluorogard cartridges with sales during the previous two years
                  before the effective date of this Agreement.

                  From Bedford Molding:
                  --------------------

                  . 16908       Slipper
                  . 40640       ILM
                  . 41641       ILM
                  . 42172       HF Top Cap
                  . 42173       HF Bottom Cap
                  . 43014       LHVD Hsg Bowl
                  . 43015       LHVD Hsg Head
                  . 95977       CMP End Cap
                  . 95978       CMP End Cap
                  . 95979       CMP End Cap
                  . 108318      CMP Slipper
                  . 108184      LHVD Potting Disk
                  . 108488      Solaris C-ring
                  . 108489      Solaris Solid Ring
                  . 108995      Filter Guide
                  . 108996      Filter Guide
                  . 108997      Pivot
                  . 108998      Latch Slide
                  . 108999      Release Tab

                  From Jaffrey Molding:
                  --------------------

                  . 12596X2     Halar disk
                  . 15051       1/4" VCR protective cap
                  . 15050       3/8" VCR protective cap
                  . 12597       Endcap
                  . 12598       Endcap
                  . 15122X1     WWFG 1" Dustcap (red)
                  . 15122X2     WWFG 1" Dustcap (clear)
                  . 16946X      PFA cap CD 0
                  . 15121X2     Mini-WWFG dustcap
                  . 12747       Endcap
                  . 13290       Adapter Dbl o-ring
                  . 95894       Housing inlet cap
                  . 95895       Housing outlet cap
                  . 16040       Hsg outlet 1/4 NPTF
                  . 16041       Hsg outlet 1/2 NPTM
                  . 16042       Hsg inlet 1/4 NPTF
                  . 16043       Hsg inlet 1/2 NPTM
                  . 15411X2     Dust cap  clear WWFG
                  . 12797       Caplug NPT Wafergard

                                       9
<PAGE>

                  . 15315       Int o-ring adapt Halar
                  . 43014       LHVD IntelliGen Hsg bowl
                  . 43015       LHVD IntelliGen Hsg head
                  . 108491      Solaris end cap

                  Other BioP Assemblies Used In MiE Products:
                  -------------------------------------------

                  . 108898X3    Pegasus Subassy
                  . 108898X7    Pegasus Subassy
                  . 108898X8    Pegasus Subassy
                  . 12676       Slit Patapar
                  . 95049       Chempure Pleated Cart
                  . 12418       Cartridge Wafer-6 w/2-012
                  . Molsheim    Engineering Filter Housing's
                    Engineered  assembly equipment for
                    Systems     microelectronics applications*
                    Plant

Initial Price
for All Products:   Millipore Standard Cost as of the effective date of this
                    Agreement as set forth in Millipore's Oracle System, plus
                    ten percent of such standard cost.

* Because this Product is not an exclusively Mykrolis product, Section 7(A) of
this Agreement does not apply with respect to this Product.

                                      10

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