The Stokke Sleepi bed mattress is made of durable PU foam known for its elastic and pressure resistant qualities. The foam has grooves on the bottom side to maximize air flow. This firm mattress has a softly padded quilted cotton easy to remove cover with stretch mesh underneath. This along with the grooves and perforated bed bottom provide excellent air circulation so that your baby can sleep comfortably. Additionally, it is rolled for compact shipping making it easy to pack, fit into your car, and for transport.