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 5935-01-245-1921
NSN 5935-01-659-6162
NSN 6650-01-333-3646
NSN 7035-01-578-0644
NSN 6220-00-225-5795
NSN 5996-00-470-7762
NSN 5895-01-350-4484
NSN 5855-01-033-1375
NSN 6145-01-459-7837
NSN 5950-01-371-2095
NSN 5996-00-974-9583
NSN 5965-01-578-6260