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 6220-01-102-5003
NSN 6645-00-994-6664
NSN 5945-01-163-8683
NSN 4140-00-513-1089
NSN 6620-01-401-5356
NSN 5930-01-275-0314
NSN 5920-01-531-4575
NSN 5925-00-090-7403
NSN 5935-00-045-9832
NSN 7035-00-104-7613
NSN 5965-00-905-5197
NSN 6135-01-185-3614