1 Exhibit 5.1 February 14, 2000 Instron Corporation 100 Royall Street Canton, MA 02021 Re: 13 1/4% Senior Subordinated Notes Due 2009 ------------------------------------------ Ladies and Gentlemen: We are acting as counsel for Instron Corporation, a Massachusetts corporation (the "Company"), in connection with the proposed issuance of up to $60,000,000 aggregate principal amount of the Company's 13 1/4% Senior Subordinated Notes due 2009 (the "Exchange Notes"), and the guarantees of the Exchange Notes (the "Subsidiary Guarantees" and, together with the Exchange Notes, the "Securities") by certain subsidiaries (the "Subsidiary Guarantors") of the Company, in exchange for its 13 1/4% Senior Subordinated Notes due 2009, and the guarantees of such notes by the Subsidiary Guarantors (the "Original Securities"). Reference is made to (i) the Company's Registration Statement on Form S-4 (the "Registration Statement") with respect to the Securities, to be filed with the Securities and Exchange Commission under the Securities Act of 1933 (the "Securities Act"), (ii) the Indenture, dated as of September 29, 1999 (the "Indenture"), among the Company, the Subsidiary Guarantors and Norwest Bank Minnesota, National Association, as Trustee (the "Trustee"), pursuant to which the Securities will be issued in exchange for the Original Securities, and (iii) the Registration Rights Agreement, dated as of September 29, 1999, among the Company, the Subsidiary Guarantors and Donaldson, Lufkin & Jenrette Securities Corporation (the "Registration Rights Agreement"). In rendering this opinion, we have assumed that the signatures on all documents examined by us are genuine. We have examined such documents, records and matters of law as we have deemed necessary for purposes of this opinion, and based thereupon, but subject to the limitations set forth below, we are of the opinion that: 1. The Exchange Notes, when duly executed by authorized officers of the Company, authenticated by the Trustee, and issued in accordance with the Indenture and the Registration Rights Agreement, will be binding obligations of the Company, entitled to the benefits of the Indenture, except to the extent enforceability may be limited by bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors' rights generally and general equitable principles (whether considered in a proceeding in equity or at law). 2 Instron Corporation February 14, 2000 Page 2 2. The Subsidiary Guarantees, when duly executed and delivered by authorized officers of the Subsidiary Guarantors, authenticated by the Trustee, and issued in accordance with the Indenture and the Registration Rights Agreement, will be binding obligations of the Subsidiary Guarantors, entitled to the benefits of the Indenture, except to the extent enforceability may be limited by bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors' rights generally and general equitable principles (whether considered in a proceeding in equity or at law). The opinions expressed herein are expressly limited to the federal laws of the United States of America and the laws of the State of New York, as currently in effect, and we express no opinion as to the effect of, or the enforceability under, the laws of any other jurisdiction. We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to us under the caption "Legal Matters" in the Prospectus constituting a part of the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act. Very truly yours, /s/ Jones, Day, Reavis & Pogue