NOTE: The grade designations used herein for Grades A and B do not include reference to the specified minimum yield strength. Other grade designations used herein comprise the Letter A or X followed by the first two digits of the specified minimum yield strength. Coverage. This specification covers seamless and welded steel line pipe. It includes standard-weight and extra-strong threaded line pipe; and standard-weight plain-end. regular-weight plain-end. special plain-end. extra-strong plain-end. and double-extra-strong plain-end pipe; as well as bell and spigot and through-the-flowline (TFL) pipe. Dimensional requirements on threads and thread gages. stipulations on gaging practice. gage specifications and certification. as well as instruments and methods for inspection of threads are given in API Std 5B and are applicable to products covered by this specification. Grades covered by this specification are A25@ A@ B@ X42@ X46@ X52@ X56@ X60@ X65 and X70 and grades intermediate to the Grades X42 and higher listed. The chemical composition and mechanical properties of intermediate grades which are subject to agreement between purchaser and manufacturer must be consistent with the corresponding requirements for the grades to which the material is intermediate. Pipe manufactured as Grade X60 or higher shall not be substituted for pipe ordered for Grade X52 or lower without purchaser approval. Policy. American Petroleum Institute (API) specifications are published as an aid to procurement of standardized equipment and materials. These specifications are not intended to inhibit purchasers and producers from purchasing or producing products made to specifications other than API. and nothing in any API specification is intended to in any way inhibit the purchase of products from companies not authorized to use the API monogram.* Nothing contained in any API specification is to be construed as granting any right@ by implication or otherwise@ for the manufacture. Sale@ or use in connection with any method@ apparatus or product covered by letters patent@ nor as insuring anyone against liability for infringement of letters patent. API specifications may be used by anyone desiring to do so@ and every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them. However the Institute makes no representation@ warranty or guarantee in connection with the publication of any API specification and hereby expressly disclaims any liability or responsibility for loss or damage resulting from their use@ for any violation of any federal@ state or municipal regulation with which an API specification may conflict@ or for the infringement of any patent resulting from the use of an A PI specification. The use of the API monogram is a warranty by the manufacturer to the purchaser that the manufacturer has obtained a license to use the monogram and@ Further@ that the product which bears the monogram conforms to the applicable API specification. The marking requirements@ including the API monogram. are an integral part of API specifications Products purchased to API specifications must be marked in accordance with the requirements of the marking section of the appropriate specification. However@ the American Petroleum Institute does not represent@ warrant or guarantee that products bearing the API monogram do in fact conform to the applicable API standard or specification. * The API monogram - AP - is a registered trademark of the American Petroleum Institute.