This 20mm (ID) aluminum sealing washer is used on nearly all Guzzis from 1967 until today. It is commonly used on the large engine oil drain plug, but is also used on many engine oil fill plugs, and on many models for the transmission filler and rear (final) drive fill plug. It was also used on the V700, Ambassador, and Eldorado in the cylinder head, to seal the 12 o'clock cylinder stud access plug. It's best to use a new one of these crush washers at every oil change. Replacement for the old number fiber washer 90714195.