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 5895-01-435-2552
NSN 4140-01-034-5867
NSN 7035-01-603-2836
NSN 6135-00-985-7846
NSN 5999-00-246-7084
NSN 6650-01-406-7141
NSN 5990-01-382-5364
NSN 6150-00-356-4330
NSN 5920-01-467-9477
NSN 5905-01-422-2597
NSN 7035-01-655-5081
NSN 4140-00-111-3247