Dream On Me Twinkle star 117-Coil Crib and Toddler Mattress features a heavy-duty innerspring with a firm infant side featuring CertiPUR-US certified layers for comfort. Flex Edge provide extra side edge support and safety when 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 steels coils for maximum durability and support, and 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.