Polyester [REJUVENATE YOUR OLD MATTRESS] Adding a 4 inch memory foam mattress topper to your overly SOFT mattress can make the mattress more durable, comfortable, and prolong the lifespan of your full mattress. [PERFECT BALANCE OF SOFTNESS & SUPPORT] This medium firm mattress topper combines gel memory foam and bamboo charcoal foam to balance the comfort and support you need during the sleep. It also can conform to your body curve and relieve pressure points.