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                                                                    EXHIBIT 4.11

                               GUARANTY AGREEMENT


         THIS GUARANTY AGREEMENT ("Guaranty") is executed effective the 14th day
of April, 2000 by each of the persons, firms, corporations, partnerships or
other entities listed on the signature pages hereto under the heading
"Guarantors" (collectively, whether one or more, "Guarantors", and each
individually a "Guarantor"), in favor of Weatherford International, Inc., a
Delaware corporation (the "Creditor").

                              W I T N E S S E T H:

         WHEREAS, for the purpose of enabling the Obligor (as hereinafter
defined) to obtain credit or other accommodations from Creditor, Guarantors have
agreed to guarantee jointly, severally and unconditionally to Creditor the
prompt payment when due of the Subordinated Promissory Note (as hereinafter
defined);

         NOW, THEREFORE, in consideration of the credit and financial
accommodations extended or to be extended to the Obligor, by and for other good,
fair and valuable considerations and reasonably equivalent value, the receipt
and sufficiency of which are hereby acknowledged, the Guarantors hereby agree as
follows:

                     ARTICLE I--NATURE AND SCOPE OF GUARANTY

         Section 1.01. Guaranty of Obligation. Guarantors hereby irrevocably,
jointly and severally, and unconditionally guarantee to Creditor and Creditor's
respective successors and assigns, when due (and howsoever such due date or
maturity shall arise), the due and punctual payment in United States Dollars of
the Guaranteed Obligations (as that term is hereinafter defined). Guarantors
hereby irrevocably and unconditionally covenant and agree that each is jointly
and severally liable for the Guaranteed Obligations as primary obligor.
Guarantors hereby acknowledge and agree that the financial accommodations to be
made to Obligor pursuant to the Subordinated Promissory Note will materially
benefit the Obligor and the Guarantors, and in recognition of this fact,
Guarantors desire to guarantee the payment of any and all indebtedness,
obligations and liabilities to Creditor and its successors and assigns arising
under or in connection with the Subordinated Promissory Note.

         Section 1.02.  Definitions.

         (a) As used herein, the following capitalized terms shall have the
following meanings:

         "Creditor" shall have the meaning first set forth therefor hereinabove.

         "Debtor Laws" means any federal or state bankruptcy, insolvency,
reorganization, moratorium, fraudulent transfer, fraudulent conveyance,
preferential transfer or similar law or judicial decision, relating to or
affecting the enforcement of creditors' rights generally.


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         "Default" means the occurrence of any breach, default, violation or
event of default under the Subordinated Promissory Note.

         "Subordinated Promissory Note" means the Subordinated Promissory Note
made by the Obligor to the order of the Creditor, dated of even date herewith,
in the original principal amount of $100,000,000.

         "Guaranteed Obligations" means all principal of and accrued unpaid
interest on the Subordinated Promissory Note, and all other indebtedness,
obligations, and liabilities of Obligor to Creditor at any time arising under or
otherwise evidenced by the Subordinated Promissory Note, and all reasonable
costs, expenses and fees, including, without limitation, court costs and
reasonable attorneys' fees, arising in connection with the enforcement or
collection (whether or not any proceeding is commenced in connection therewith)
of any or all amounts, indebtedness, liabilities and obligations arising in
connection with the Subordinated Promissory Note.

         "Guarantor Claims" means all debts, obligations and liabilities of the
Obligor, to any of the Guarantors, whether such debts and liabilities now exist
or are hereafter incurred or arise, or whether the obligations of Obligor
thereon be direct, contingent, primary, secondary, several, joint and several or
otherwise, and irrespective of whether such debts or liabilities be evidenced by
notes, contracts, open account, or otherwise.

         "Lien" means any lien, charge, encumbrance, security interest,
mortgage, deed of trust or other right or claim against property, real or
personal, tangible or intangible, that secures the indebtedness or obligations
of a Person.

         "Obligor" means Grant Prideco, Inc., a Delaware corporation, and other
affiliates of Grant Prideco, Inc. that the Guarantors and Creditor may agree
upon in writing from time to time.

         "Person" means any person, firm, corporation, partnership (limited or
general), association, joint venture, trust, individual, limited liability
company or other similar entity.

         Section 1.03. "Obligor" to Include New Corporations. The term "Obligor"
as used herein shall include any successor corporation, partnership, association
or other successor entity.

         Section 1.04. Payment by Guarantors. If all or any part of the
Guaranteed Obligations shall not be punctually paid by the Obligor when due,
whether at maturity or earlier by acceleration or otherwise, Guarantors shall,
immediately upon demand by Creditor, and without presentment, protest, notice of
protest, notice of non-payment, notice of intention to accelerate, notice of
acceleration or any other notice whatsoever, pay in lawful money of the United
States of America, the amount due on the Guaranteed Obligations to Creditor at
Creditor's principal office as Creditor shall indicate. Such demand(s) may be
made at any time coincident with or after the time for payment of all or part of
the Guaranteed Obligations are due, but not punctually paid, and may be made
from time to time with respect to the same or different items of Guaranteed
Obligations.

         Section 1.05. No Duty to Pursue Others. It shall not be necessary for
Creditor (and each of the Guarantors hereby waives any rights which Guarantors
may have to require Creditor), in order to enforce such payment by any of the
Guarantors, first to (i) institute suit or exhaust its

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rights against Obligor, or other Persons or any of them now or hereafter liable
on the Guaranteed Obligations, (ii) enforce Creditor's rights against any
security which shall ever have been given to secure the Guaranteed Obligations,
(iii) enforce Creditor's rights against any other guarantors of the Guaranteed
Obligations, (iv) join Obligor, or any other Persons now or hereafter liable on
the Guaranteed Obligations in any action seeking to enforce this Guaranty, or
(v) exhaust any rights available to Creditor against any security or guarantor
which shall ever have been given to secure the Guaranteed Obligations. Creditor
shall not be required to take any other action to reduce, collect or enforce the
Guaranteed Obligations.

         Section 1.06. Waiver of Notices, etc. Each of the Guarantors agrees to
the provisions of the Subordinated Promissory Note, and, except as specifically
set forth in this Guaranty, hereby waives notice of (i) any loans or advances by
Creditor to or at the request of Obligor, (ii) acceptance of this Guaranty,
(iii) any amendment, modification, extension for any period, increase,
refinancing or rearrangement of the Guaranteed Obligations or any supplement,
modification, amendment and/or restatement of the Guaranteed Obligations or of
the Subordinated Promissory Note, (iv) the occurrence of any breach by Obligor,
or any default, under the Subordinated Promissory Note with respect to any of
the Guaranteed Obligations, (v) Creditor's transfer or disposition of the
Guaranteed Obligations, or any part thereof, and (vi) protest, proof of
non-payment or default by Obligor.

         Section 1.07. Nature of Guaranty. This Guaranty is an irrevocable,
unconditional and absolute guaranty of payment and performance and not a
guaranty of collection. This Guaranty may not be revoked by any of the
Guarantors and shall continue to be effective with respect to any Guaranteed
Obligations arising or created after any attempted revocation by any of the
Guarantors. This Guaranty shall remain in full force and effect until all of the
Guaranteed Obligations have been paid in full. This Guaranty may be enforced by
Creditor and by any subsequent holder or holders of the Guaranteed Obligations
and shall not be discharged by the assignment or negotiation of all or part of
the Guaranteed Obligations. The liability of the Guarantors under this Guaranty
shall be irrevocable, absolute and unconditional irrespective of any change in
the time, manner or place of payment of, or in any other term of, all or any
part of the Guaranteed Obligations or the Subordinated Promissory Note, or any
other amendment, waiver of or any consent to changes in the Subordinated
Promissory Note.

         Section 1.08. Payment of Expenses. In the event that any of the
Guarantors breaches or fails to timely perform any provisions of this Guaranty,
each of the Guarantors agrees to pay to Creditor all reasonable costs and
expenses (including court costs and reasonable attorneys' fees) incurred by
Creditor in the enforcement hereof or the preservation of Creditor's rights
hereunder.

                       ARTICLE II--EVENTS NOT DISCHARGING
                           ANY GUARANTORS' OBLIGATIONS

         Each of the Guarantors consents and agrees to each of the following,
and each of the Guarantors further agrees that each of the Guarantors'
obligations under this Guaranty shall not be released, diminished, impaired,
reduced or adversely affected by any of the following:

         Section 2.01. Modifications, etc. Any renewal, extension for any
period, increase, amendment, modification, alteration, supplement or
rearrangement of all or any part of the Guaranteed Obligations, or of the
Subordinated Promissory Note or understandings or

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agreements between Obligor or Creditor, or any other Persons, pertaining to the
Guaranteed Obligations.

         Section 2.02. Adjustment, etc. Any adjustment, indulgence, forbearance
or compromise that might be granted or given by Creditor to Obligor, or any one
or more of the Guarantors or any other guarantor of the Guaranteed Obligations.

         Section 2.03. Condition of Obligor or Guarantors. The insolvency,
bankruptcy, arrangement, adjustment, composition, reorganization, liquidation,
disability, dissolution or lack of power of Obligor, or any other Person now or
hereafter liable for the payment of all or part of the Guaranteed Obligations,
including any of the Guarantors; or any sale, lease or transfer of any or all of
the assets or properties of Obligor, or any one or more of the Guarantors or any
other guarantor of the Guaranteed Obligations, or any changes in the
shareholders, partners, members or other composition of Obligor, or any one or
more of the Guarantors.

         Section 2.04. Preference. Any payment by Obligor to Creditor is held to
constitute a preference under Debtor Laws or for any reason or Creditor is
required to refund such payment or pay such amount to Obligor or to any other
Person.

         Section 2.05. Release of Obligor. Any full or partial release of the
liability of Obligor on the Guaranteed Obligations or any part thereof, or any
other Person now or hereafter liable, whether directly or indirectly, jointly,
severally, or jointly and severally, to pay, perform, guarantee or assure the
payment of the Guaranteed Obligations or any part thereof, it being agreed by
each of the Guarantors that any of the Guarantors may be required to pay the
Guaranteed Obligations in full without assistance or support of any other
Person, and none of the Guarantors has been induced to enter into this Guaranty
on the basis of a contemplation, belief, understanding or agreement that
Creditor will look solely to other Persons to perform the Guaranteed
Obligations.

         Section 2.06. Security. The taking or accepting of any security,
collateral or guaranty, or other assurance of payment, for all or any part of
the Guaranteed Obligations.

         Section 2.07. Incorporation/Merger. The reorganization, merger or
consolidation of Obligor, into or with any other corporation, partnership or
other entity, Person or form.

             ARTICLE III--REPRESENTATIONS, WARRANTIES AND COVENANTS

         To induce Creditor to enter into the Subordinated Promissory Note, each
of the Guarantors represents, warrants and covenants to Creditor that:

         Section 3.01. Authorization. Each of the Guarantors has full power and
authority to execute and deliver this Guaranty and to consummate the transaction
contemplated hereby. This Guaranty has been or will be duly authorized and
approved by all necessary and proper action of Guarantors. This Guaranty
constitutes a legal, valid and binding obligation of Guarantors, and when
executed and delivered, will constitute a legal, valid and binding obligation,
enforceable against Guarantors in accordance with its terms, except as limited
by Debtor Laws. The execution, delivery and performance by each of the
Guarantors of this Guaranty and the consummation of the transactions
contemplated hereunder do not, and will not, breach or violate

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any law to which any of the Guarantors is subject or constitute a default under,
or result in the breach of or violate, any material agreement to which any of
the Guarantors is a party.

         Section 3.02. Familiarity and Reliance. Each of the Guarantors is
familiar with, and has independently reviewed books and records regarding, the
financial condition of Obligor; however, none of the Guarantors are relying on
such financial condition, on any representation or warranty by the Creditor, or
on any collateral, as an inducement to enter into this Guaranty.

         Section 3.03. Benefit. Each of the Guarantors derives benefit from its
relationship with the Obligor in connection with the ownership and operation of
the business of the Obligor and its subsidiaries, and as a result thereof, each
of the Guarantors has received, or will receive, direct or indirect benefit and
reasonably equivalent value from the making of this Guaranty.

                            ARTICLE IV-MISCELLANEOUS

         Section 4.01. Guarantor Claims. EACH OF THE GUARANTORS EXPRESSLY AND
SPECIFICALLY POSTPONES IN EFFECT ANY AND ALL RIGHTS, WHETHER ARISING BY LAW OR
AGREEMENT OR OTHERWISE, TO REIMBURSEMENT, CONTRIBUTION, SUBROGATION, EXONERATION
AND INDEMNIFICATION, AND TO PARTICIPATE IN ANY CLAIM OR REMEDY OF CREDITOR OR
ANY OTHER PERSON AGAINST OBLIGOR, OR ANY OTHER PERSON, WITH RESPECT TO THE
GUARANTEED OBLIGATIONS, UNTIL SUCH TIME AS CREDITOR HAS BEEN FULLY AND FINALLY
PAID.

         Section 4.02. Waiver. No failure to exercise, and no delay in
exercising, on the part of Creditor, any right hereunder shall operate as a
waiver thereof, nor shall any single or partial exercise thereof preclude any
other or further exercise thereof or the exercise of any other right. The rights
of Creditor hereunder shall be in addition to all other rights provided by law.

         Section 4.03. Notices. Except for telephonic notices permitted herein,
any notices or other communications required or permitted to be given by this
agreement, the Subordinated Promissory Note or any other documents and
instruments referred to herein must be (i) given in writing and personally
delivered or mailed by prepaid certified or registered mail, or (ii) made by
telecopy delivered or transmitted, to the party to whom such notice of
communication is directed, to the address of such party as follows: (a) if to
Guarantors, at the address set forth on the signature page hereof, and (b) if to
Creditor, then at Creditor's chief executive office or, if different, as
expressly set forth in any other written document executed by Creditor and any
Obligor.

         Section 4.04. Entirety and Amendments. This Guaranty embodies the
entire agreement between the parties and supersedes all prior agreements and
understandings, if any, relating to the subject matter hereof and this Guaranty
may be amended only by an instrument in writing executed by the parties hereto.

         Section 4.05. Parties Bound; Assignment, Duration. This Guaranty shall
be binding upon and inure to the benefit of the parties hereto and their
respective successors, assigns and legal representatives. This Guaranty shall
continue in full force and effect in accordance with the terms hereof, and may
not be terminated by the unilateral act of any of the Guarantors.

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         Section 4.06. Multiple Parties. Any Person signing this Guaranty shall
be bound thereby, whether or not any other party signs this Guaranty or is
released therefrom at any time. It is specifically agreed that Creditor may
enforce the provisions hereof with respect to one or more of the Guarantors
without seeking to enforce the same as to all or any other such parties, and
each of the Guarantors hereby waives any requirement of joinder of all or any
other of the other parties hereto in any suit or proceeding to enforce the
provisions hereof. The obligations created by this Guaranty shall be joint and
several (and not merely joint) with respect to each of the Guarantors.

         Section 4.07. Headings. Section headings, subheadings and captions are
for convenience of reference only and shall in no way affect the interpretation
of this Guaranty.

         Section 4.08. Multiple Counterparts. This Guaranty may be executed in
any number of counterparts, all of which taken together shall constitute one and
the same agreement, and any of the parties hereto may execute this Guaranty by
signing any such counterpart.

         Section 4.09. Choice of Law. This Guaranty shall be governed by and
construed in accordance with the internal laws of the State of Texas.

         Section 4.10. Severability. In the event that any one or more of the
provisions contained in this Guaranty should be held invalid, illegal, or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions contained herein shall not in any way be affected or
impaired thereby.


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         EXECUTED effective as of the date first written above.


                               GUARANTORS:

                               GRANT PRIDECO TECHNOLOGY, INC.

                               By: /s/ Linda S Bubacz
                                  -----------------------------------------
                                       Linda S. Bubacz
                                       President

                               Address:

                               1450 Lake Robbins Drive, Suite 600
                               The Woodlands, Texas  77380




                               GRANT PRIDECO, LP

                               By:  Grant Prideco Holding, LLC, a Delaware
                                    limited liability company, general
                                    partner of Grant Prideco, LP

                               By:  Grant Prideco, Inc., a Delaware corporation,
                                     sole member of Grant Prideco Holding,
                                     LLC


                               By: /s/ John C. Coble
                                   -----------------------------------------
                                       John C. Coble
                                       President

                               Address:

                               1450 Lake Robbins Drive, Suite 600
                               The Woodlands, Texas  77380


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