A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6150-01-205-0566
NSN 5920-01-307-3866
NSN 5915-00-917-3608
NSN 6320-01-232-4664
NSN 5925-01-005-9481
NSN 5945-00-192-6086
NSN 6320-01-129-9656
NSN 5965-01-519-1929
NSN 6620-01-565-2341
NSN 7035-01-014-3808
NSN 6650-01-116-9731
NSN 6685-01-384-3979