Fit & Design: One size fits most Wide, reinforced cuff Padded heel and toe Heating system built-in with accessible battery pouch to control heat Recessed heating element to prevent abrasion Insert the battery into the battery pouch with the terminal up - the terminal must fit into the top connection when the pouch is closed To turn on, snap the pouch closed to activate the heat; to turn off, un-snap the pouch. Remove battery from the pouch when not in use and before storing Technology: Battery powered with 9B cell alkaline batteries and rechargeable batteries Additional Details: Recommended care: Remove batteries and hand wash in warm water with gentle detergent. Do not bleach, machine dry, iron, or wring. Gently squeeze excess water from socks and hang to dry. Avoid pulling on sock from the cuff Warning: this product should not be used by diabetics, persons with extreme circulatory problems, or any person who may be sensitive to the application of direct heat to the skin's surface. If in doubt, consult your physician prior to using