There is no water to add, no water to boil, no dripping packs and no towels to prepare. Moisture is drawn from the humidity in the air and Retained in a specially designed 100% cotton cover. When the hot pack is turned on, the Retained moisture is rapidly heated by high-grade ceramics, forcing the moisture out of the flannel cover onto the patient's skin, allowing deeper penetration of heat into the body's tissue. The moisture acts only as a means to transmit heat more deeply into the tissue, so only a small amount is needed. Theratherm, Unlike all competitive products on the market, has a digital hand control allowing the operator to program The following parameters: treatment temperature, treatment time and on/off. Competitive units, including thermophore, require the operator to make continual contact with a single-loaded switch to generate and maintain heat from the pad. This is positioned as a safety feature. Theratherm has a conventional on/off control switch. Automatic time control (1 - 60 min. Timer) with auto SHUT off. please note our return policy. For health and hygienic reasons this product is not Returnable once used.