Self-tapping, oversized drain plug, to be used when the threads have become damaged or stripped. Tapered fitting, which seals on the threads, as opposed to being sealed with a washer.
Fitting instructions: This plug is tapered, and must be fitted by using it as an engineering tap. Half a turn in and half a turn out again so it cuts its own thread. The plug will not go all the way in and should stop short of the hexagonal head. Therefore no washer is required. Never over tighten the bolt as it can crack the alloy casing.