The Heat Factory Pocket Sock has a special pocket over the toes to hold Heat Factory Foot Warmers. Simply insert a Foot Warmer packet in the pocket and enjoy 6 hours of soothing warmth. The sock has a cushioned arch and reinforced heel, and is above calf length. One pair of Heat Factory Foot Warmers included (additional wamers sold separately). 93% acrylic, 7% polyester.