In crushing practice, these rates are (1) based on crusher dimensions, wherein the largest cube that will enter is compared with the largest that can be discharged, or (receiving opening) / (discharge opening); the receiving opening is measured from the top of the movable member to the top of the stationary member; and (2) based on actual products; (a) overall reduction ratio = (mean size of feed) / (mean size of product); (b) individual reduction ratio = (size most abundant in feed) / (mean size of grading band concerned).