A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6320-00-389-4756
NSN 5975-01-363-8875
NSN 5910-00-228-4487
NSN 5965-01-538-0698
NSN 5855-01-027-8414
NSN 5945-01-260-2539
NSN 5930-01-249-5632
NSN 4140-01-652-0207
NSN 5855-00-885-8452
NSN 5915-01-321-3234
NSN 5998-01-598-7424
NSN 5999-01-546-3670