The Serta Sheer Slumber 8" Medium Firm Gel Memory Foam Mattress-In-A-box delivers quality, convenient comfort to your front door in our smallest carton ever. We've combined cooling Serta Gel Memory Foam with our durable Serta Foam Core for a cool, supportive mattress that keeps you in dream-land all night long.2" of our gel memory foam contours to your body for cradling comfort and allows airflow to help keep you cool and restful all night longA thick layer of our Serta Foam Support Core (no coils) provides a medium firm feel and durable support for any sleep positionConsistent edge to edge support is provided by our Foam Support CoreWe've used new compression technology to package your mattress in our smallest carton yet