Kiribai Mysterious Socks That Don't Let Your Feet Get Cold The fabric on the skin side is made of the insulating Air Heat fiber used in the series. By making it a cover sock shape, it wraps the entire sole of the foot from the "toe" to the "heel" and traps heat, so the warmth lasts. Since it's the type to be worn inside tights, it's not noticeable, allowing you to take measures against cold feet while staying fashionable. I am selling it because I haven't used it. The size is 22-25cm. Thank you. This item can be shipped immediately.