The QUAD 5 SIDE is a premium support system providing a 5-zoned ergonomic design with reinforced max resistant coil edge support on each side of the mattress for edge-to-edge support and comfort. By utilizing 2 zones of firmer coils under your lower back and knees, the system provides targeted support where it is needed most. The other 3 alternating sections are designed to give less resistance to help maximize conformance and pressure relief at the shoulders, hips and feet.