... ,6.8,8.8,9.8... ..... Copper MACHINE SCREW, brass shoulder bolt screw ,BRASS ALLEN SCREW. ... screw;Type "M","UNC","UNF","BSW"threads for Machine threads.Head typesHexagon head,Mushroom head,Pan head ... Head is much thicker ,it is strong not break down . meanwhile,socket is much deeper,it is convenient ... most of places such as drywall,concrete,chipboard,machine,wood...2) Main export market:North America, ...