① Material ：SKH51 Hardness ：59-61HRC Length：within 300mm Coaxiality ：ф0.01mm Max. precision： 0.005mm ② Material ：SKD61 Internal Hardness ：38-42HRC Surface Hardness ： HV900 and higher Length： 1000mm and lower Coaxiality：ф0.06mm Max. precision 0.01mm The internal holes of these products have been subjected to precision grinding and rigid coaxiality control to ensure proper fitness with ejector pin and core as well as high compatibility.