A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5935-01-612-0031
NSN 5910-00-296-8816
NSN 7035-00-763-6180
NSN 6620-01-598-2271
NSN 5960-01-423-2511
NSN 5975-01-269-7885
NSN 5998-01-448-8139
NSN 5925-01-530-5757
NSN 6135-01-413-4747
NSN 6620-01-641-4122
NSN 6150-01-431-9727
NSN 5990-01-180-7365