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 5950-01-410-2925
NSN 5925-00-574-4362
NSN 6105-00-373-3780
NSN 7035-00-206-6123
NSN 5910-01-461-7800
NSN 5998-01-497-7899
NSN 5996-01-223-3506
NSN 5855-00-918-1622
NSN 6220-00-085-5206
NSN 6150-00-899-0740
NSN 5965-00-973-1090
NSN 5935-01-504-6205