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 5905-01-069-3419
NSN 4140-01-463-2529
NSN 5895-01-243-9651
NSN 6610-01-494-9853
NSN 5910-01-056-5111
NSN 5999-01-549-0285
NSN 5950-01-595-4071
NSN 5935-01-420-1591
NSN 5930-00-528-9728
NSN 5855-00-688-9954
NSN 5945-01-495-6564
NSN 6145-01-549-2089