These socks are a blend of wool and acrylic to keep your feet warm, even when the battery is off! One 9v battery on the cuff of each sock provides warmth for up to 5 hours with a non rechargeable battery or up to 3 with a rechargeable battery. (Batteries not included.) Wiring runs the length of the socks to the toes to put the heat where it is most needed. As these are very low wattage they are best used for keeping warmed feet comfortable longer rather than heating already cold feet. For longest life hand wash after removing batteries and lay socks flat to dry. Specs: 68% acrylic, 19% polyester, 12% wool, 1% rubber