BIG HEAD,SPECIAL HEAD SCREW 1.ISO,ANSI,JIS, ... 6.8,8.8,9.8.. BIG HEAD,SPECIAL HEAD SCREW,WHITE PHILLIPS HEAD SCREW . A good non-standard ... 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 ... % ,is higher hardness than other.2.Fasteners' Head is much thicker ,it is strong not break ...