Sleep Master 8-Inch Gel Memory Foam Mattress, Twin Mattress layers include: 2" Gel memory foam, 2" pressure relief foam, and a 4" high-density foam base Gel infused memory foam provides a cooler nights sleep The mattress is shipped in a small box and can take up to 48 hours to fully expand from its compressed state CertiPUR-US Certified; Scent: Memory foam mattresses are often associated with having a distinct odor Limited 5 year warranty; Scent: Evergreen is a green tea extract that naturally neutralizes odors from day one. made with Green Tea, ActivFRESH Charcoal, and Natural Plant Oil to naturally keep your mattress fresh