A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6110-01-090-0804
NSN 6610-01-539-9084
NSN 5935-01-461-7008
NSN 6320-00-336-5570
NSN 5975-01-436-1013
NSN 6645-01-025-1002
NSN 6610-00-331-3460
NSN 6150-00-528-4175
NSN 6320-01-320-3305
NSN 5835-00-467-7294
NSN 2925-00-523-0322
NSN 6650-01-143-4586