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 5950-01-174-4015
NSN 5950-00-432-0292
NSN 5930-01-199-2920
NSN 6240-00-960-0224
NSN 5905-01-461-0091
NSN 6685-01-555-4820
NSN 6110-01-079-6332
NSN 7035-00-631-3782
NSN 7035-00-104-7613
NSN 5950-00-917-0689
NSN 5996-01-218-5678
NSN 6650-01-217-9375