QRC-4D Number of Rails: 4 Rail Cart Features: -4 Rail Cart holds up to 64 bins and accepts 6 sizes of Ultra Bins.-7 Rail Cart holds up to 112 bins and accepts 3 smallest sizes of Ultra Bins.-800 lb load capacity. Dimensions: -Dimensions for 4 Rail Cart: 35 1/2" H x 24" W x 36" D.-Dimensions for 7 Rail Cart: 35 1/2" H x 18" W x 36" D.