Flex-Phonesâ¢ Indestructible Foam Headphones HamiltonBuhl Flex-Phonesâ¢ 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. Best of 2015 Scholastic Teacher's Pick Flex-Phonesâ¢ are certified for all major USA and international child safety testing standards. We are extremely proud that they have been awarded the Scholastic Teacher's Pick as "The Best Of 2015". Recommended for children ages 3 and up, Flex-Phonesâ¢ deliver high quality sound that will never exceed 85 decibels, ensuring young developing ears are protected. Most importantly, the extremely clear sound quality will never exceed 85 decibels, ensuring young developing ears are protected. Flex-Phones are packaged with a snap-on extension band for smaller children â just snap on the extension band for a snugger fit.