Exhibit 5.1

ONE SHELL PLAZA 910 LOUISIANA HOUSTON, TEXAS 77002-4995 TEL      +1 713.229.1234 FAX      +1 713.229.1522 www.bakerbotts.com AUSTIN DALLAS DUBAI HONG KONG HOUSTON LONDON MOSCOW NEW YORK RIYADH WASHINGTON

January 12, 2006

Westlake Chemical Corporation

2801 Post Oak Boulevard, Suite 600

Houston, Texas 77056

Ladies and Gentlemen:

Westlake Chemical Corporation, a Delaware corporation (the “Company”), has requested that we render the opinions expressed below in connection with the Company’s proposed offering of $250,000,000 aggregate principal amount of 6 ⁵/8% Senior Notes Due 2016 (the “Notes”) and related subsidiary guarantees (the “Subsidiary Guarantees”) pursuant to the Registration Statement on Form S-3 (Reg. No. 333-124581) filed by the Company and the subsidiary guarantors named in Schedule I hereto (the “Subsidiary Guarantors”) with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “1933 Act”), which relates to the offering and sale of various securities from time to time pursuant to Rule 415 under the 1933 Act.

In our capacity as your counsel in the connection referred to above, we have examined originals, or copies certified or otherwise identified, of (i) the Amended and Restated Certificate of Incorporation and the Amended and Restated Bylaws of the Company, each as amended to date (together, the “Charter Documents”); (ii) the charters or bylaws or other organizational documents, as applicable, of each of the Subsidiary Guarantors; (iii) the Senior Indenture and the form of Supplemental Indenture relating to the Notes (each as filed as an exhibit to the Current Report on Form 8-K reporting the offering of the Notes (the “Form 8-K”), and, together, the “Indenture”); (iv) the prospectus supplement dated January 10, 2006 that the Company prepared and filed with the Commission on January 11, 2006 pursuant to Rule 424(b)(5) under the 1933 Act; (v) the underwriting agreement dated January 10, 2006 among the Company, the Subsidiary Guarantors, and Deutsche Bank Securities Inc., Banc of America Securities LLC, J.P. Morgan Securities Inc. and Credit Suisse First Boston LLC (collectively, the “Underwriters”) relating to the offering and sale of the Notes and the Subsidiary Guarantees (the “Underwriting Agreement”); and (vi) the corporate records of the Company and the Subsidiary Guarantors, certificates of public officials and of representatives of the Company, including minute books of the Company and the Subsidiary Guarantors as furnished to us by the Company, statutes and other instruments and documents as a basis for the opinions hereinafter expressed. In giving such opinions, we have relied upon certificates of officers of the Company and of public officials with respect to the accuracy of the material factual matters contained in such certificates. In giving the opinions below, we have assumed that the signatures on all documents examined by us are genuine, that all documents submitted to us as originals are accurate and complete, that all documents submitted to us as copies are true

and correct copies of the originals thereof and that all information submitted to us was accurate and complete.

On the basis of the foregoing, and subject to the assumptions, limitations and qualifications hereinafter set forth, we are of the opinion that the Notes and the Subsidiary Guarantees will, when duly executed by the Company and the Subsidiary Guarantors, issued and authenticated by the trustee in accordance with the terms of the Indenture and duly purchased and paid for by the Underwriters in accordance with the terms of the Underwriting Agreement, constitute legal, valid and binding obligations of the Company and the Subsidiary Guarantors, respectively, enforceable against the Company and the Subsidiary Guarantors, respectively, in accordance with their respective terms, except as the enforceability thereof is subject to (i) any applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent transfer or conveyance or other laws relating to or affecting creditors’ rights generally and (ii) general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

The opinions set forth above are limited in all respects to matters of the laws of the State of New York, the General Corporation Law of the State of Delaware, the Delaware Revised Uniform Limited Partnership Act and applicable federal law.

We hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Form 8-K reporting the offering of the Notes. We also consent to the reference to our Firm under the heading “Legal Matters” in the prospectus forming a part of the Registration Statement referred to above. In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the 1933 Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ Baker Botts L.L.P.

SCHEDULE I

POTENTIAL SUBSIDIARY GUARANTORS

Name	Jurisdiction of Incorporation or Organization
Geismar Holdings, Inc.	Delaware
GVGP, Inc.	Delaware
North American Bristol Corporation	Delaware
North American Pipe Corporation	Delaware
Van Buren Pipe Corporation	Delaware
Westech Building Products, Inc.	Delaware
Westech Profiles Limited	Delaware
Westlake Chemical Holdings, Inc.	Delaware
Westlake Chemical Investments, Inc.	Delaware
Westlake Chemical Manufacturing, Inc.	Delaware
Westlake Chemical Products, Inc.	Delaware
Westlake Development Corporation	Delaware
Westlake International Corporation	Delaware
Westlake Management Services, Inc.	Delaware
Westlake NG I Corporation	Delaware
Westlake NG II Corporation	Delaware
Westlake Olefins Corporation	Delaware
Westlake Petrochemicals LP	Delaware
Westlake Polymers LP	Delaware
Westlake PVC Corporation	Delaware
Westlake Resources Corporation	Delaware
Westlake Styrene LP	Delaware
Westlake Vinyl Corporation	Delaware
Westlake Vinyls Company LP	Delaware
Westlake Vinyls, Inc.	Delaware
WPT LP	Delaware