When sourcing aluminum oxide balls, the most critical factor is the Alumina Content (Al2O3 percentage), which typically ranges from 92% to 99.7%. Higher purity levels offer superior wear resistance and chemical stability. You must also verify the Bulk Density (should be >3.60g/cm³ for 92% alumina) and Mohs Hardness (typically 9), as these determine the grinding efficiency and lifespan of the media. For precision applications, check the Sphericity and Diameter Tolerance to ensure uniform grinding results.