A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5998-00-426-0321
NSN 5835-00-958-6231
NSN 5915-00-175-8657
NSN 6320-01-143-3597
NSN 6135-01-430-3119
NSN 5999-00-087-6042
NSN 5996-01-379-7978
NSN 5905-01-421-3338
NSN 5930-01-240-8872
NSN 2925-01-446-6976
NSN 6685-01-152-2846
NSN 6320-01-369-5014