Serta's Perfect Sleeper Special Edition Firm Mattress has individually wrapped coils, which react to each contour of the body. Packing up to 30% more steel support into this special coil gauge design and creating a more firm feel across the complete mattress surface, the Perfect Sleeper Special Edition Firm Mattress also features Serta's advanced Best Edge® Foam Encasement. This extra-deep foam rail combined with the advanced innerspring system, allows the sleeper full breadth of the mattress for sleeping. Edge to edge comfort with reduced edge roll-off grants the extension to the sleep area for freedom and the space to move. First, the Cool Twist® Gel Memory foam, which is designed to conform to the body gently. Working with the complete mattress system, it resides in the upholstery layer to provide that pressure-relieving comfort that is so refreshing. In addition, its unique design assists with enhanced airflow through the mattress itself. Then, there is also a layer of Serta® Balanced Support Foam. This new foam provides a "just right" mixture of comfort and support. This combination is responsible for that great Serta cushioning comfort and enhanced support.