Crushers and mills reduce solid products to a desired particle or aggregate size in dry or slurry forms. In addition, mills are used for mixing and dispersing solids within liquids. Selection criteria for crushers and mills should be based on feed size, material, and hardness. Processing equipment types include ball or media mills, cone and gyratory crushers, disk attrition mills, colloid and roll mills, screen mills and granulators, pin mills, impact mills and breakers, hammer and cage mills, jaw crushers, jet and fluid energy mills, roll crushers, disc mills, and vertical rollers and dry pans.