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 5910-01-463-9061
NSN 5990-01-439-4343
NSN 5935-00-632-5228
NSN 6620-00-364-6890
NSN 5915-00-045-9071
NSN 5950-01-507-1107
NSN 5835-01-142-9233
NSN 5935-01-281-7512
NSN 6135-01-396-4900
NSN 6610-00-288-5655
NSN 6130-01-555-6935
NSN 6135-01-022-5427