A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 4140-01-608-0199
NSN 6685-00-234-3394
NSN 6130-00-334-0691
NSN 5905-01-045-2373
NSN 6620-01-044-3371
NSN 5895-01-486-1922
NSN 5915-01-066-4791
NSN 5905-01-574-7417
NSN 5990-01-463-5400
NSN 6145-00-141-8095
NSN 5935-00-868-1531
NSN 5999-00-594-3412