A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5999-00-249-1780
NSN 6150-00-094-2664
NSN 5945-00-466-2249
NSN 5855-00-925-7887
NSN 5998-00-111-0893
NSN 5990-00-578-8850
NSN 5905-01-310-5423
NSN 6135-00-209-6918
NSN 5855-01-423-9921
NSN 5925-01-509-3524
NSN 6150-00-292-6131
NSN 6105-01-215-2339