Memory foam mattress: Get a Shell cool touch memory foam mattress. Bonnell spring: A 13.5 gauge open coil Bonnell spring unit with a layer of next gen visco-elastic memory foam. Cool touch: The memory foam is activated by your body heat, meaning it contours to your body shape. Anti-allergy: Made with hypoallergenic and anti-dust mite filling for a cleaner, healthier sleep environment. Five sizes: Choose between small single, single, small double, double or king sizes.