... 8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the specification of our Products ? MaterialsCarbon ... customer's demand .Threads/ScrowsType "M","UNC","UNF","BSW"thread are available. Head typesHexagon head,Mushroom head,Pan head,Countersunk ... used in most of places such as drywall,concrete,chipboard,machine,wood...2)Main export market:North America,South America, ...