A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6610-01-080-1041
NSN 5935-01-381-0824
NSN 4140-01-140-0966
NSN 5905-01-026-7049
NSN 6650-01-159-0224
NSN 5998-00-302-5283
NSN 6130-00-957-8661
NSN 5985-00-479-0460
NSN 6145-01-573-7994
NSN 6145-00-262-3345
NSN 5930-01-547-7472
NSN 7035-01-026-1171