Terramar Battery sock (1 Pack) 71% Acrylic/19% Polyester/10% Wool Imported 9V battery for long life Reinforced toe and heel All day comfort. The sock will generate warmth, it is not design to make the feet hot. Battery snap pouch pocket for battery storage Wool blend for superior moisture management Heel and toe reinforced for durability When hand washing do not wring sock simply hang or let flat to dry All over cushion for shock, absorption and abrasion prevention