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 5895-01-280-7119
NSN 6145-01-355-9300
NSN 5935-00-983-5291
NSN 6650-01-207-0829
NSN 6240-00-753-2031
NSN 6110-01-485-9081
NSN 5910-01-476-5044
NSN 5905-00-987-1541
NSN 5930-01-325-0598
NSN 5985-01-519-1359
NSN 6135-00-968-8594
NSN 5975-00-469-1443