The Hot Chillys Kids' Elite Heat Mid Volume Ski Socks are made from a nylon blend for strength, durability and heat. Lightweight hollow fibers embedded with permanent oxide minerals harness the body's far infrared energy to generate gentle warmth. Active Carbon embedded into fibers provides enhanced thermal regulation and odor blocking properties. The Hot Chillys Kids' Elite Heat Mid Volume Ski Socks are mid volume for a little extra cushioning in your little ones' boots.