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 5895-01-620-6554
NSN 5895-01-245-9090
NSN 2925-00-174-4322
NSN 5990-01-151-8756
NSN 6610-01-027-1641
NSN 6650-00-495-8710
NSN 2925-00-601-4173
NSN 5925-01-250-8447
NSN 6620-01-290-2973
NSN 5905-01-544-2162
NSN 5905-00-242-8964
NSN 6105-00-900-8990