These are the stones with built-in heating elements that provide soothing hot stone massages, unlike typical stones that must be heated for hours and cool quickly. Ideal for soothing sore muscles or relaxing trigger points during a massage, each is made from a fire-kilned clay with a heating element that averages 130º, the optimal temperature for hot stone therapy. Warming in less than a minute, each stone stays hot for up to two hours from a four-hour charge of its lithium-ion battery using the included AC adapter. Only one side of each stone warms up for comfort while handling by a massage giver; can be used on the skin with creams, oils, or lotions or over clothing. Includes two stones and AC chargers. Box 9 1/4" L x 6" W x 3" D. (2 1/2 lbs.)