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 5999-01-044-3931
NSN 5950-01-313-6591
NSN 5960-01-460-7620
NSN 5920-01-475-5234
NSN 5985-01-082-9424
NSN 6220-01-050-8122
NSN 2925-00-071-4197
NSN 6650-01-451-1372
NSN 4140-00-457-2510
NSN 7035-01-386-5722
NSN 6320-01-583-6809
NSN 5990-00-683-1095