This specification covers Grade C-75 seamless steel casing and non-upset and external-upset tubing@ in the sizes and wall thicknesses shown in the standard lists (Tables 1.1 and 1.2)@ and the dimensional tables (Tables 6.1 through 6.6). It also includes requirements for couplings and thread protectors. 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. Although this specification@ in conjunction with API Std 5B@ permits manufacturers authorized to use the API monogram on round-thread casing to manufacture and apply the monogram to buttress and extreme-line casing@ considerable skill and know-how is required for the tooling for@ and machining of@ these joints. Therefore@ any manufacturer who desires to produce these joints is advised to consult with manufacturers who have produced these joints before attempting their manufacture. NOTE: This specification is tentative and the API monogram cannot be applied to pipe covered by this specification. Nothing contained in this specification is to be construed as granting any right@ by implication or otherwise@ for 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. This specification is for the convenience of purchasers and manufacturers in ordering and producing pipe and is not intended to inhibit purchasers and producers from purchasing and producing pipe meeting specifications other than those contained herein nor is it intended in any way to inhibit purchasers from purchasing pipe from companies not authorized to use the API monogram.