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 6105-01-418-0824
NSN 5910-01-395-5030
NSN 5985-00-155-5991
NSN 6610-01-228-8883
NSN 5998-00-578-8582
NSN 5920-01-335-6347
NSN 5945-00-515-2667
NSN 6110-00-702-9460
NSN 6650-01-376-6965
NSN 6240-00-828-6228
NSN 6150-01-300-2187
NSN 7035-01-435-4009