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 6105-01-463-8557
NSN 5835-01-201-7363
NSN 5935-00-875-7904
NSN 5965-01-443-5490
NSN 6105-00-477-6880
NSN 5855-01-147-4785
NSN 6650-01-465-5362
NSN 6650-00-585-1850
NSN 6620-00-017-8098
NSN 2925-01-455-2558
NSN 6650-00-698-5869
NSN 6145-00-469-8657