Grinding Media is cylindrical, with equal length and diameter for maximum surface area. The media material used with the grinding products is Burundum alumina or Zirconia. Ultra-high fired Burundum alumina with 3.42 specific gravity is ideal for most milling and has low contamination. Burundum is supplied in 10lb (5kg) packages. Premium high-density 5.55 specific gravity Zirconia mills faster than Burundum, with less wear of grinding jars and media. Zirconia is sold in 5lb (2kg) packages.