A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 4140-01-498-5854
NSN 6650-00-944-1399
NSN 6150-01-167-9706
NSN 5998-00-768-0807
NSN 5905-01-541-5437
NSN 6105-01-557-1219
NSN 5925-01-365-5442
NSN 5905-00-904-5853
NSN 6685-01-483-4819
NSN 6240-01-291-4833
NSN 6650-01-364-4616
NSN 5920-01-009-1307