... )material:mild steel,45# steel,40Cr steel 2)surface:z.p,black,hot dip... 3)size:M8-M48 4)grade:4 ... .8,10.9,12.9 bolt m12x1.5, centre bolt 10.9, hex centre bolts with nutCertificate: ISO9001:2000High Quality Strengthen: Grade ... you have any questions, please feel free to contact me. centre bolts