12.9 bolt grades: 1.Spec:DIN,JIS,ASTM,GB,UIC 2.Surface:black, HDG 3.Grade:4.8, ... 8.8,10.9,12.9 4.Material:Q235 ... GB Standard High strength 12.9 bolt grades with large hexagon head for steel structures I. Item:High strength bolts ... III. Usage:Supply to railway, highway, bridge, boiler with steel structure, industry workshop, high civil buildings, hoisting machinery ...