A washer or cone or disk shape with a centrally located hole, designed to accommodate a flat or oval head screw and provide additional bearing area on the material being fastened. It may or may not have a flush flange feature.
NSN 6110-01-346-0671
NSN 6135-00-990-1822
NSN 5999-01-024-2907
NSN 5985-00-699-5817
NSN 7035-00-371-7749
NSN 5975-01-090-1062
NSN 5985-01-332-0632
NSN 6240-01-618-1978
NSN 5950-00-717-6729
NSN 5930-01-029-0808
NSN 6145-01-041-3057
NSN 6105-00-881-2268