The RPO-M Series plugs provide dual seals on ISO fluid power system metric ports. An integral O-ring-type bead seals snugly into the bevel of the threaded opening to prevent oil or fluid leakage. A 12-point head makes it possible to tighten with socket or wrench. : : A:.41, B:.44, C:.97, TOFITTHRSZ: 18 x 1.5.