Taken from the Heat In a Click website:
"Heat in a Click was first established in London, England in 2005. Over the years, Heat in Click has become a leader the heating pads arena. Heat in a Click is the fastest growing heating pads company in the world, with almost 200 distributors in 43 countries. Along with our standard line, the company is capable of producing custom-made heating pads, including your personal preference of label and design.
Our products are instantaneous, portable and reusable heating pads. At a click of a button, the pad will reach 54c (130f) degrees. The content of the products is non-toxic, comprising of Sodium Acetate, a salt based solution and water. By flexing the small metal disc inside the pad, a molecular reaction is started causing the solution to crystallize. During the reaction (changing its state of aggregation from liquid to crystal form), energy is released in the form of heat. The heating process can be re-initiated and the pack re-used again and again.
All of our products are design to serve our customers in their day to day lives. The products are environmental friendly, recyclable and unless damaged, can be used indefinitely; we have taken the well being of the environment into serious consideration."