Why just sleep when you can Sierra Sleep With the Sierra Sleep Hybrid 1400 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. Hypoallergenic material is ideal for sufferers of allergies for ultimate undisturbed sleep not to mention peace of mind. Plus this mattress arrives in a box for quick and easy setup. Simply remove the plastic wrap and unroll. Foundationbox spring available sold separately.