Flex-Phones Indestructible Foam Headphones HamiltonBuhl Flex-Phones are nearly indestructible, made from a single piece of EVA foam. EVA foam is safe, non-toxic, BPA-free, soft and an extremely flexible material. Flex-Phones are certified for all major USA and international child safety testing standards. Recommended for children ages 3 and up, Flex-Phones are packaged with a snap-on extension band for smaller children, just snap on the extension band for a snugger fit. Most importantly, the extremely clear sound quality will never exceed 85 decibels, ensuring young developing ears are protected.