Pair these cooling vest packs with Chill-Its 6255 Lightweight Phase Change Cooling Vest (not included) to keep workers cooler, safer and more productive. The phase change cooling material in the packs maintains a 59-degree Fahrenheit (15-degree Celsius) temperature for up to 2 hours when activated. Lightweight packs quickly recharge in as little as 5 minutes. Grid design eliminates stiffness for more flexibility while you work.