Push-Back racking systems use a series of mobile carts that ride on rails within each pallet row. A loaded pallet is placed on the upper cart within the system. When another loaded pallet is loaded into the same bay, it pushes back the first loaded pallet. This process continues until all the trays (usually 3-4) are utilized. This system offers a highly dense storage solution when space is at a minimum and when the total amount of product to be stored is small and consistent in size and weight. The disadvantages are similar to that of Drive-In and Double Reach Systems the pick selectivity is reduced, FIFO issues are compromised, and there is potential of lost pallet positions due to height loss caused by the systems carts.