When a tomato sorter is used for tomato sorting it sorts based on the sizes of the tomatoes. The size is determined as well as the length of the tomato with the sorter.  Even the diameter of the tomato is measured. It is important that all of sorting criteriea are taken into account because otherwise there could be very different tomatoes being grouped together. Tomatoes come in such a variety of sizes that it is essential that they not just be measured by the length because some tomatoes can be long and slender. The slender tomatoes may not be good for certain applications.  For instance, burger shops may require a rounder tomato because they fill up the surface of the burger more precisely.