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 5965-00-823-8623
NSN 5915-01-193-5152
NSN 6150-01-210-9204
NSN 5930-01-202-7926
NSN 6650-01-127-9518
NSN 5935-00-319-4788
NSN 7035-01-118-5861
NSN 6650-01-392-2204
NSN 6110-00-246-3941
NSN 5998-00-910-8772
NSN 5945-01-323-7171
NSN 6685-01-363-9688