The Simmons ultra-firm crib mattress has a tencel cover made from eucalyptus using an eco-friendly production process that does not harm the environment. It is the newest fabric technology to come from the adult bedding industry with exceptional qualities. Its superb breathability, excellent moisture absorption and natural anti-bacterial properties will provide your baby with a dry and cool sleep environment that stays fresh and clean. The ultra-firm thermo bonded polyester core is 2 sided with a firm side for infants and a comfort layer on the toddler side (after 12 months) for a more comfortable sleep surface for your growing toddler. The core is 99.9% VOC free and breathable and combined with the tencel cover gives your baby a healthy and luxurious sleep environment. The cover is water and stain resistant. Great for toddler beds too!