Neck & Lower Back Therapy Bundle includes: 1 X Neck & Shoulder Therapy 1 X Lower Back Pad 1 X Medium Therapy Rectangle (5"x3.5") With the snap of a button our warmers heat up, and stays warm from 30 minutes to approx. 2 hours without the risk of over heating or burning before gradually cooling down to room temperature. The ideal temperature is reached in just a few seconds. No batteries or microwave needed! Use it anywhere, anytime! Non-toxic and best of all they can be used hundreds of time! Reusable Heat Pads not only provide instant heat but are really neat to watch. Inside the pouch is a supersaturated mix of sodium acetate and water. This liquid state just needs one thing to set it off, and when you click the metal disc inside, you start the reaction. Immediately, sodium acetate crystals start to form around the disc, precipitating outward. As they do, they release all that pent-up energy in an exothermic reaction. And voila. Heat. Boiling the Reusable Heat Pads conveys the energy back into that supersaturated solution. You could repeat this cycle infinitely theoretically, only this is the real world and eventually the outside layer is going to wear down which ends the cycle.
