12 inch Sierra Sleep hybrid king mattress NEW AY-M62841Retail price $1885. With the Sierra Sleep Hybrid 1200 king mattress, you have endless possibilities for restful sleep. Feel the support of a truly traditional coil mattress which contours to your body for a comforting feel. High density foam provides the firmness you love. Gel memory foam provides restorative support for your lower back. Plus, this mattress arrives in a box for quick and easy setup. Simply remove the plastic wrap and unroll.