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 6110-00-808-4121
NSN 6135-01-128-5358
NSN 5915-00-763-8124
NSN 5835-01-381-2683
NSN 6220-00-823-6688
NSN 5999-00-930-1931
NSN 5835-01-498-9410
NSN 6645-01-336-3647
NSN 2925-01-525-2892
NSN 6620-01-575-9561
NSN 5998-00-684-8186
NSN 2925-01-257-6225