A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6685-00-188-1991
NSN 5905-01-458-2413
NSN 5835-00-148-9719
NSN 6110-00-986-3244
NSN 6150-01-109-2266
NSN 6650-00-952-2754
NSN 5996-01-463-8197
NSN 5905-01-408-6226
NSN 4140-01-231-5031
NSN 4140-01-221-1383
NSN 4140-01-437-8715
NSN 5996-00-392-7626