Manufactured in accordance with accepted standards and conform to the specifications shown below. The latest issue of any specification shall constitute the authority. Standard Malleable Iron Fittings. Fed. Spec. WW-P-521E. Amer. Std. A.S.A. B-16.3 (Dimensions) A.S.A. B-2.1 (Pipe Threads) Ferrous Plugs, Bushings and Locknuts A.S.A. B16.14 Fed. Spec. WW-P-471. A.S.A. B-2.1 (Pipe Threads).