CYLINDER HEAD SCREW,BRASS 1.ISO,ANSI,JIS,DIN ... :4.8 ,6.8,8.8,9.8... CYLINDER HEAD SCREW,BRASS COPPER DECORATIVE SCREW,SMALL SCREW . A ... Machine threads.Head typesHexagon head,Mushroom head,Pan head,Countersunk head,Bugle head,Oval head,Hex flange head,Round head,Ball head,Button head...Socket typesPhillip ... 23% ,is higher hardness than other.2.Fasteners' Head is much thicker ,it is strong not break down ...