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 5945-01-489-5519
NSN 6220-01-281-6027
NSN 5920-00-436-0780
NSN 5930-00-771-3801
NSN 6320-01-576-6310
NSN 5990-00-038-6482
NSN 5920-01-088-5944
NSN 5998-00-238-0294
NSN 7035-01-656-9650
NSN 6145-01-262-4781
NSN 6105-01-430-3214
NSN 5999-01-453-5707