The wool blend Battery Sock ensures all day warmth and comfort. A Velcro pouch holds the 9V battery and the toes and heel are reinforced for durability.Specifications and Features: Wool blend fabric All over cushioning 9 Volt battery power Chafe-free toe seam 1-Pair Pack 71% Acrylic, 19% Polyester, 10% Wool Machine Wash Warm. Wash with Similar Colors. Do not Bleach. Tumble Dry Low. Do not Iron.