1.Life more than 3Ys, with circulation repair use. 2.After Vacuum Heat Treatment, HRC 60~63. 3.Suface roughness overmatch Ra0. 1.The material is SKD11,which import from Japan2.After Vacuum Heat Treatment, HRC 60~633.Suface roughness overmatch Ra0.14,Life more than 3Ys, with circulation repair use Step pulley(SKD11)