J.w. Winco 742-32-m26x1.5-os-2 aluminum threaded plug with 2mm vent hole with m26 x 1.5 thread gn 742 fill/drain plugs are fitted with outside diameter d1 to fit screw holes with bsp threads included in din 3852. The seal is retained in a groove undercut in the mating face, which prevents it from dropping out and from extruding when the plug is tightened. For this reason the seal can be of a softer material which offers better sealing. Maximum heat resistance: 180c (356f).