The Casper Onyx mattress is designed with 3 layers of foam for comfort, breathability and support. Obsessively engineered by Casper's award-winning research and development team, this mattress contains Breathe Flex Foam for support and pressure relief & Breathe Foam for air flow that pairs breathability with softness for all-night comfort. Key features include a cozy knit cover designed with added stretch so you can experience all the comfort your mattress has to offer. Features a top layer of Breathe Flex Foam that's both responsive and breathable to soothe you to sleep with the perfect bit of bounce. A firm Casper Core base provides long-lasting support while preventing sinking and sagging. Foams are certified by the CertiPUR-US program, meaning they are made without ozone depleting chemicals and regulated by the Consumer Product Safety Commission Low VOC (Volatile Organic Compound) emissions for indoor air quality (less than 0.5 parts per million).