Used on agavgapache attack helicopter. washer, rivet, flat rivet diameter is 0.188". thickness is 0.032 plus/minus 0.003. material: steel (carbon) spec. mil-s-7952 or qq-s-698, cold rolled, half or full hard; or sae 1010 (commercial) cold rolled, half or full hard. finish: steel-cadmium plate per qq-p-416, type ii, class 2. note: these washers are intended primarily for use with solid rivets in plastics. do not use these washers where washers on nas 1149 will meet design requirements. cadmium surface treated