Selective pallet racking structures are the most commonly used of all pallet rack types. They are the most versatile because every pallet position (SKU) has aisle access for full pallet or case pick. More access, however, means less density because of numerous aisles. In pallet rack systems, the more selectivity you have, the less density of the pallets stored (number of pallets deep). Conversely, the more density you have, the less selectivity of the pallets stored (access from aisle)