The Chill-Its 6220 Rechargeable Phase Change Cooling Vest Ice Packs keep workers cooler, safer and more productive. These charge packs are compatible with the 6215, 6225, 6230 6235 cooling vests, sold separately. The phase change cooling material maintains a 64° F (18° C) temperature for up to four hours when activated. Simply place the two removable packs in a cooler of ice water for 10 minutes; freezer for 15 minutes; refrigerator for 25 minutes; or near an air conditioner for one to two hours. Then place the recharged cooling packs in the vest pockets for hours of cooling.