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 5910-01-652-8456
NSN 6220-01-090-0126
NSN 5920-00-546-5624
NSN 5975-01-268-1945
NSN 6620-00-079-0311
NSN 5999-00-813-5646
NSN 5950-01-134-7409
NSN 6150-00-812-8145
NSN 6130-00-147-4657
NSN 5996-01-264-8463
NSN 5855-01-042-7990
NSN 6105-00-580-9417