... as :Self tapping threads "A","AB", Threads for chipboard screw,wood screw,drywall screw;Type "M","UNC","UNF","BSW"threads for Machine threads ... head,Hex flange head,Round head,Ball head,Button head...Socket typesPhillip type,Pozi type,Eleven type,hexagonal type,Torx type ... is much thicker ,it is strong not break down . meanwhile,socket is much deeper,it is convenient to tighten by screwdriver ...