Chill-Its 6260 S/M Black Lightweight Phase Change Cooling Vest with PacksErgodyne Ei 12133 Designed to be 30% 60% lighter weight than other cooling vests on the market, the Chill Its Lightweight Phase Change Cooling Vest keeps workers cooler, safer and more productive. Its 100% biodegradable phase change cooling material maintains a 59 F 15 C temperature for up to two hours when activated. Constructed with a polyester cotton blend fabric, the vests adjustable hook and loop closures around the waist provide a customized fit