A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 4140-00-113-1009
NSN 6110-01-578-6777
NSN 5910-01-098-4061
NSN 4140-00-223-5197
NSN 5935-01-056-5494
NSN 5915-01-442-4245
NSN 6105-00-847-8199
NSN 5925-01-129-9074
NSN 5975-00-596-2119
NSN 6240-00-578-6820
NSN 5905-01-114-1801
NSN 6685-01-321-5895