Keep your sensitive materials at the right temperature. High-tech phase change formula is ideal for products requiring an accurate, consistent temperature ? returns to gel state when thawed. Soft cold packs are manufactured with laminated, metallized film exterior to resist punctures and provide a radiant heat barrier. Phase change formula lasts 15 percent longer that standard gel packs four formulations from 32 to -10?f (0 to -23?C) nontoxic and reusable.