A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6240-00-079-1759
NSN 5915-01-227-2337
NSN 6620-01-554-6571
NSN 4140-00-410-2581
NSN 6650-01-298-4138
NSN 6220-00-557-8861
NSN 5935-01-093-7900
NSN 5945-00-934-9045
NSN 5920-01-050-3341
NSN 5925-01-310-7662
NSN 5985-00-455-7275
NSN 5965-00-864-8046