... screw,drywall screw;Type "M","UNC","UNF","BSW"threads for Machine threads.Head typesHexagon head,Mushroom head,Pan head,Countersunk head ... each year ISO Quality person come into factory for Supervising inspecting. "integrity, in accordance with the national standards, do not ... used in most of places such as drywall,concrete,chipboard,machine,wood...2) Main export market:North America,South America, ...