The 8.5 inch Roxbury was specifically designed to give you a comfortable night’s rest using an open-cell structure of ventilated memory foam which allows heat to escape and air to flow around the body, creating a more comfortable and universal sleep. A patented support system is built into the entire length of the mattress giving it a very unique feature that makes it stand alone in comparison with other memory foam mattresses in this size and all comparisons to the Tempurpedic Classic, Original, Deluxe line of mattresses. All of our mattresses are 5 lbs of density and up, we do not stock 4lb mattresses because they do not hold up - so please only compare densities when comparing mattresses. Also, The Roxbury is our most popular mattress when used with our adjustable bed systems.