... ,6.8,8.8,9.8..... 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 are available.Carton steel ... 10B21,1035,CH38F,1039,40ACR...Alloy steel are 35,40CrMo,SCM435,10B38...Stainless steel is SS201,202,302,304, ...