A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5950-01-238-0509
NSN 5930-01-486-6750
NSN 6130-01-639-8149
NSN 5920-01-470-3810
NSN 6110-01-259-2616
NSN 5998-01-243-6926
NSN 5999-01-632-6221
NSN 5965-00-594-3115
NSN 5998-00-601-0673
NSN 5996-01-137-6008
NSN 5975-01-155-1661
NSN 6105-01-600-0366