A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6150-00-041-5038
NSN 5930-01-081-7936
NSN 6150-01-619-9818
NSN 6620-01-423-0833
NSN 6320-01-390-5385
NSN 5965-01-425-5857
NSN 5999-01-030-7826
NSN 5905-00-262-5156
NSN 6135-01-142-2417
NSN 6130-00-302-7823
NSN 2925-01-250-2731
NSN 6610-00-365-4454