... :4.8 ,6.8,8.8,9.8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the specification of ... ,CH38F,1039,40ACR...Alloy steel are 35,40CrMo,SCM435,10B38...Stainless steel is SS201,202,302,304,316...copper is shiny ... a professional manufacturer with more than 20 years experiences in screw,bolt,nut,washer,rivet, stud, pin,wrench and so on .2 ...