A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6650-01-550-6328
NSN 2925-00-275-1807
NSN 5985-01-029-1655
NSN 5895-01-043-2620
NSN 6150-01-520-6332
NSN 5999-01-256-0077
NSN 6320-01-056-1164
NSN 5905-00-906-5781
NSN 5975-01-058-9099
NSN 5855-01-388-2424
NSN 2925-01-204-6243
NSN 6645-01-354-7624