This specification covers seamless and welded steel@ and welded wrought-iron casing and tubing@ seamless steel drill pipe@ also (as tentative) seamless and electric-welded steel liners. It includes ;:regular and internal-upset easing with short or long threads; plain-end liners; non-upset and external-upset tubing; and internal-upset@ external-upset@ and internal-external- upset drill pipe-in the sizes and wall thicknesses applicable to the various grades of pipe as shown in the standard lists (Tables 1 through 4)@ and in the dimensional tables (Tables 9 through 16). Dimensional requirements on threads and gages@ and stipulations on gaging practice also are covered@ as well as requirements for couplings and thread protectors. 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.