Anvil 8700132155, Steel Pipe Fitting, Cap, 3/8" NPT Female, Black Finish Cap for closing and terminating the end of a pipe or fitting Female National Pipe Taper (NPT) threads for connecting to a male pipe or fitting Made from steel for greater rust resistance than iron NPT threads for creating tighter seals than straight threads Meets specifications ASTM A53 and ASME B 1.20.1 for quality assurance