A new oil drain valve for the very popular Briggs & Stratton lawnmower motors is now available in our shop. The thread size is NPT 3/8 "-18. It is known that NPT threads, which are slightly conical, seal over the thread. No sealing ring is required here. These threads are mainly used in American products. The same thread can be found Incidentally, also in American aircraft engines and can also be used here.