A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6220-01-422-1429
NSN 6240-01-345-4479
NSN 4140-01-350-4475
NSN 6220-01-010-3958
NSN 5990-01-007-9483
NSN 5999-00-509-8807
NSN 6240-01-621-7646
NSN 5915-00-232-3387
NSN 7035-01-458-3532
NSN 5950-00-009-8799
NSN 5930-00-201-5105
NSN 6650-01-049-5361