... 8,9.8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the specification of our Products ? MaterialsCarbon steel ... Mushroom head,Pan head,Countersunk head,Bugle head,Oval head,Hex flange head,Round head,Ball head,Button head... Socket ... ,good technology1.We are a professional manufacturer with more than 20 years experiences in screw,bolt,nut,washer,rivet, stud, pin,wrench ...