Anvil 3/8" Black Union 150#. This malleable iron union features a ground joint for a secure connection between two pipes of the same size. Its black finish resists rust, while the National Pipe Threads ensure tighter seals than straight threads. Meets Fed. Spec. WW-P-471-B, ANSI B-16.14 (Dimensions), ANSI B-2.1 (Pipe Threads), Ferrous Plugs, Bushings, and Locknuts, Fed. Spec. WW-P-471-B, ANSI B-16.14 (Dimensions), ANSI B-2.1 (Pipe Threads), Malleable Iron Unions (Class 150), Fed. Spec. WW-U-531C, ANSI B-16.39.