A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6645-01-335-5845
NSN 5925-01-223-4803
NSN 5990-01-493-4039
NSN 5930-01-528-7970
NSN 6610-01-649-5326
NSN 5998-01-561-7945
NSN 5965-01-200-6613
NSN 6150-00-233-6356
NSN 6610-00-854-0975
NSN 5895-01-221-4377
NSN 6135-01-313-4865
NSN 6130-00-881-2272