Coverage. This specification covers seamless and welded steel line pipe. It includes standard weight and extra strong threaded pipe; and standard weight plain-end@ regular-weight plain-end@ special plain-end@ extra-strong plain-end@ and double-extra strong plain-end pipe. The sizes and wall thicknesses applicable to the various processes of manufacture under this specification are indicated in the dimensional tables herein. 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. Grade X60 or higher pipe (API Std 5LX) shall not be substituted for pipe ordered to this specification 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 API 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. 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