Hollow Bolt,Stainless 1.ISO,ANSI,CE,JIS,DIN,BS& non-standard ... .Grade:4.8 ,6.8,8.8,9.8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the specification of ... professional manufacturer with more than 20 years experiences in screw,bolt,nut,washer,rivet, stud, pin,wrench and so on .2 ...