A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5930-01-078-0977
NSN 5915-01-028-6880
NSN 6650-01-632-3501
NSN 6685-00-760-6032
NSN 6610-01-122-0064
NSN 5945-00-811-7379
NSN 5965-00-208-4896
NSN 5998-01-423-3130
NSN 7035-01-013-9889
NSN 6145-01-321-2334
NSN 4140-00-155-8012
NSN 5910-01-460-8562