This document discusses different types of pallet rack systems that are suitable for various warehouse needs. It describes push back racks, which utilize gravity to push pallets forward for easy access, and can provide 90% more storage than other selective systems. Drive-in racks allow pallets to be driven directly into the system for high density storage. Pallet flow racks use rollers to move pallets to the front for fast access to every product but require high pallet quality. Carton flow racks are well-suited for high volume order picking as boxes are loaded on one side and picked from the other. Cantilever racks accommodate oddly shaped materials like lumber. Selective racks provide versatile and cost-effective access to each pallet