A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 5999-01-455-0664
NSN 5960-00-153-7115
NSN 5920-01-019-6270
NSN 5930-01-199-6037
NSN 5855-00-896-4047
NSN 5910-00-131-9743
NSN 6685-01-103-8455
NSN 6240-01-602-8238
NSN 4140-01-495-4981
NSN 5990-00-296-4825
NSN 6145-01-282-8695
NSN 6220-00-707-5044