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 5915-00-190-6940
NSN 5915-01-178-0238
NSN 2925-01-510-9378
NSN 5915-01-259-5705
NSN 5910-01-386-4231
NSN 2925-01-233-8545
NSN 5920-01-397-1280
NSN 2925-01-363-5978
NSN 6145-00-196-4886
NSN 6130-01-428-3955
NSN 6130-01-578-5880
NSN 6220-01-531-1402