Pallet flow rack systems are designed for dense storage. This system uses slightly inclined roller tracks that allow pallets to move along the sloped track. The pallet flow tracks often have a built in breaking system, which controls the speed of the moving pallets. If the system is loaded from the back and unloaded from the front, the unit load rotation is first in, first out (FIFO). Pallet flow can also be used in a push back form with a first in, last out (FILO) product rotation. Each pallet flow lane will be filled with the same SKU (storage keeping unit).