A bent spring metal washer with a centrally located hole. It is designed to exert pressure axially when assembled in place.
NSN 6240-01-275-1013
NSN 5930-01-304-1855
NSN 5895-00-317-2673
NSN 7035-01-322-8180
NSN 6130-01-414-0061
NSN 5975-00-239-5571
NSN 6610-01-388-0563
NSN 7035-01-523-8664
NSN 5998-01-568-1876
NSN 6240-01-371-0978
NSN 5975-01-499-6057
NSN 5855-01-492-9795