Anvil 8700132486, Malleable Iron Pipe Fitting, Cap, 4" 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 malleable iron for tensile strength National Pipe Taper (NPT) threads for creating a tighter seal than straight threads Black finish resists rust in oil and gas applications