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 5925-01-353-1391
NSN 6620-01-182-9489
NSN 5945-01-247-7414
NSN 2925-00-315-8442
NSN 5990-00-318-3990
NSN 2925-00-739-5090
NSN 5950-00-226-2121
NSN 5950-01-093-9751
NSN 5945-01-155-2938
NSN 5920-01-063-7427
NSN 5960-01-353-5947
NSN 5998-01-644-6936