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 4140-00-739-7033
NSN 5910-01-209-9194
NSN 6110-01-382-3844
NSN 4140-01-358-3417
NSN 6105-00-228-1160
NSN 2925-01-514-9358
NSN 5960-00-763-5390
NSN 5998-00-265-1001
NSN 5855-01-611-0382
NSN 5975-01-339-0101
NSN 6240-01-216-4060
NSN 5835-01-454-5267