... Compositions Physical Features Diameter Ranges (mm) G-J-I Popular Type Economy grinding medium,suits for ... Microhardness:≥635kg/mm² 0.8-5.0 G-J-II Popular Type Good ductility and attrition resistance, ... Microhardness:≥680kg/mm² 0.8-4.0 G-J-III Wearproof TypeZirconia Glass Drops Big specific density, ... Microhardness:≥720kg/mm² 0.8-4.0 G-J-IV Bright White Type Colorless,transparent,highintensity,low ...