The Dream On Me Twinkle star 117-Coil Crib and Toddler Mattress feature a heavy-duty innerspring with a firm infant side featuring CertiPUR-US certified layers for comfort. Flex Edge provides extra side edge support and safety when the baby starts to pull up to a standing position or when the mattress is used with a toddler bed. The outer cover is made of an easy-to-clean material that helps you make sure your baby's sleeping environment stays sanitary. It features 117 heavy-duty 15 gauge sheets of steel coils for maximum durability and support and a nine-gauge border rod for extra side strength. A heavy-duty tear- and water-resistant vinyl covering protects the mattress for years of use, while vinyl edge-binding tape keeps edge seams from splitting.