A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6240-00-304-7015
NSN 5835-01-604-7489
NSN 5925-01-258-4640
NSN 6650-00-484-3616
NSN 6220-01-060-0441
NSN 5930-00-801-8202
NSN 5935-00-555-2633
NSN 6240-00-578-7894
NSN 5960-01-138-5897
NSN 5950-01-186-5562
NSN 5985-01-516-1588
NSN 6145-01-390-1580