· 4-Inch memory foam topper instantly revamps old mattress for superior sleep climate.Product Note: Please allow 24 - 72 hours for your Mattress to regain its full shape. Any memory foam will expand faster in a warmer room. In cold temperature, at delivery, your mattress may take a bit longer to return to full sized from its compressed state.The expansion time of the mattress will vary as per the surrounding· Ventilated design optimizes air flow for fresh sleep· Responsive memory foam is engineered for ideal pressure-relieving support· Sleep cool with gel infusion that helps reduce trapped body heat· CertiPUR-US certified foams, 3-year manufacturer's warranty· Product Note: Please allow up to 72 hours for the topper to rise