construction bolts and nut Class: 10.9, 12.9 grade Material: 20MnTiB, ... bolt: Treatment: HDG, Zinc, Black... Carbon steel: Grade/class 4.8, 5.8, 8.8, 10.9, 12.9... ... railways, highways, bridges, plants,etc. 2.Certificate:ISO9001:2008. 4.Also can manufacture by requirement. Steel structure hexagon head bolts ... Station Company part equipment as follows: construction bolts and nut with CE certifation