The Organic Breathable 2-Stage Crib Mattress combines breathability, waterproofing, and a 2-stage design for a safe and innovative mattress for baby. This mattress starts with a firm, flat crib mattress made from food-grade polyethylene for easy crib changing, and then we add the most hygienic breathable cover to maximize airflow. The waterproofing on the back of the cover protects the mattress from urine, spit-up, and other messes, and the 2-stage design allows the mattress to grow with your child.