A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5920-01-159-0096
NSN 5945-01-431-8124
NSN 5925-01-398-3240
NSN 5996-01-153-0531
NSN 5990-00-254-4825
NSN 7035-00-631-3782
NSN 5975-01-062-2174
NSN 6130-01-091-7767
NSN 6610-01-183-9141
NSN 6110-00-207-8862
NSN 5855-00-165-3093
NSN 5905-00-191-6456