medium balls composition in cement mills. Grinding Media & Grinding Balls Union Process, Inc. Diameter depending on the material, ranging from 0.05 mm to 2 mm for small media mills, up to 1/8" to 1" for traditional Attritors and up to ½" to 2" for ball mills Composition metallic grinding media like carbon steel, forged steel, stainless steel or chrome steel grinding balls .