The Chill-Its 6220 Rechargeable Phase Change Packs for Cooling Vests keep workers cooler, safer and more productive. These charge packs are compatible with the 6215, 6225, 6230 6235 cooling vests. The phase change cooling material maintains a 64° F (18° C) temperature for up to 4 hours when activated. *** Phase Change Packs only, Vests sold separately *** Visit the 6215 Premium FR Phase Change Vest and Packs or the 6230 Standard Phase Change Vest and Pack