... ,9.8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the specification of our Products ? MaterialsCarbon steel,Stainless steel,Alloy steel,Copper,Aluminum ... head,Bugle head,Oval head,Hex flange head,Round head,Ball head,Button head... Socket typesPhillip type,Pozi type,Eleven type ...