A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5950-00-274-2279
NSN 5835-00-985-1444
NSN 6110-00-785-7927
NSN 5855-00-933-9978
NSN 5999-01-550-9447
NSN 5990-01-584-8363
NSN 5935-01-369-4832
NSN 6685-01-442-8036
NSN 5855-01-203-4719
NSN 5855-01-062-5655
NSN 6150-01-126-3527
NSN 5920-01-592-2723