A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6650-01-186-5762
NSN 6650-01-272-3727
NSN 5920-00-607-3385
NSN 5905-01-254-9166
NSN 6130-01-417-2165
NSN 5999-01-605-9160
NSN 5975-00-915-7632
NSN 4140-00-347-6807
NSN 5835-01-595-4099
NSN 4140-01-171-8492
NSN 6135-01-514-0356
NSN 5999-00-064-9216