A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 4140-01-178-6811
NSN 6620-01-498-4780
NSN 5950-00-321-8419
NSN 5920-01-305-3613
NSN 5835-00-931-5568
NSN 5990-01-581-5103
NSN 5910-01-226-5935
NSN 6220-01-570-2197
NSN 5945-00-931-6259
NSN 6610-00-734-5976
NSN 5945-00-905-8583
NSN 6685-01-530-6200