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 6620-01-223-9025
NSN 5935-01-376-1571
NSN 6220-01-160-7249
NSN 5990-01-056-0893
NSN 6610-01-230-9971
NSN 5985-01-019-9849
NSN 6685-00-578-5951
NSN 5960-01-495-0859
NSN 5960-01-142-8170
NSN 4140-00-126-4685
NSN 5910-00-816-9842
NSN 5985-01-076-3966