Rod mills are very similar to ball mills, except they use long rods for grinding media. The rods grind the ore by tumbling within the the mill. To prevent the conditions leading to rod charge tangling, the length to diameter ratio is maintained at 1.4 to 1.6. Rod mills accept feed up to about 50 mm (2 in.) and produce a product in the size range of 3000 to 270 mm (4 to 35 mesh).