A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5895-01-154-0151
NSN 5915-01-184-4122
NSN 5855-01-645-4172
NSN 6645-01-124-1584
NSN 6620-00-406-2914
NSN 4140-01-294-4044
NSN 5930-00-526-4452
NSN 6145-01-030-3400
NSN 5925-00-299-8037
NSN 5910-01-352-3624
NSN 5945-01-255-4141
NSN 6620-01-594-0105