Made of durable polyurethane foam known for its elastic and pressure resistant qualities. Each mattress is made of durable polyurethane foam known for its elastic and pressure resistant qualities that provide children in growth the support they need and comfort they deserve. The hypoallergenic foam has a breathable structure that evaporates moisture accumulated overnight, thus preventing fungus. In addition to being quilted on top for soft comfort, the cotton mattress cover has a mesh lining in the bottom, which combined with grooves in the mattress foam provides excellent mattress ventilation.