Mizuno [Heat Generating Material] Breath Thermo Kids Animal Socks Ski Socks Size: 14-17cm Color: Gray Thank you for viewing. These socks are warm thanks to the Breath Thermo heat-generating material. My child used them 3 or 4 times. There is some slight pilling, but they are still in good condition. If you understand that these are used items, please consider purchasing them.