Material: SKH51 Hardness: 59-61HRC Length: within 300mm Coaxial: 0.001mm Accuracy: 0.005mm Material: SKD61 Inner Hardness: 38-42HRC Surface Hardness: above HV900 Length: within 1000mm Coaxial: 0.06mm Accuracy: 0.01mm These inner holes of series product are done by lapping and control coaxial rigidly, make sure that matching and interchanging inner hole, ejector and its core.