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 6610-00-276-8919
NSN 7035-01-543-4634
NSN 6145-00-937-0976
NSN 6130-00-973-7866
NSN 6620-01-449-3101
NSN 6220-00-968-6665
NSN 6620-01-375-6741
NSN 6240-00-019-5835
NSN 6105-00-930-1878
NSN 5910-01-163-4310
NSN 5965-00-764-1841
NSN 6650-01-626-4158