... .Grade:4.8 ,6.8,8.8,9.8..... Hollow Bolt,Stainless Steel Hollow Bolt,Bolt with Internal Thread.1.What’s the ... ... FinishZinc plated,Nickel plated,Dacroment Plated,chromium plated,Tin plated,Black phosphating ,anodized ,Parkerising,and Environmental Plated is used in our ...