A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 4140-01-556-7940
NSN 7035-01-607-5481
NSN 5910-01-588-5270
NSN 5945-00-455-2471
NSN 4140-01-290-9361
NSN 5915-00-336-1644
NSN 5996-00-125-0112
NSN 6105-01-413-0209
NSN 5855-00-294-7532
NSN 6135-00-016-0071
NSN 5855-01-530-0125
NSN 6135-01-286-9563