Features: 1) Standard: GB/T3632 2) Grade: 4.8S, 5.8S, 8.8S, 10.9S, 12.9S 3) GB 1228-91 steel structural purposed high-strength bolt connecting sets 4) High-strength hexagon bolts 8.8s, 10.9s, 12.9s 5) High-strength inner hexagon bolts 8.8s, 10.9s, 12.9s 6) ASTM A193, A194, A325, A490 bolts and nuts 7) Used in steel frames, steel work, high-rises, plants, highways, railways, factories, automobiles, energy, traffic, electroforming