Chill-Its 6220 Phase Change Cooling Vest Charge Packs keep workers cooler, safer and more productive when paired with compatible Ergodyne 6215, 6225, 6230 6235 cooling vests (not included). Phase change cooling material maintains a 64-degree Fahrenheit (18-degree Celsius) temperature for up to 4 hours when activated. Cooling packs quickly recharge in 10 minutes in a cooler of ice water, 15 minutes in a freezer and 25 minutes in a refrigerator. Patented honeycomb, ice pack design eliminates stiffness for more flexibility while you work. Hand-washable charge packs deliver instant cooling relief for anyone working or playing outside or indoors in warm temperatures where heat-related illnesses are possible.