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. The phase change cooling material maintains a 64° F (18° C) temperature for up to 4 hours when activated. HOW TO USE *** Phase Change Vests not included. *** There are many ways to activate your cooling vest. 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 1 to 2 hours. Then place the recharged cooling packs in the vest pockets for hours of cooling. Cooling vests are perfect for anyone in need of instant cooling relief while working or playing outside or indoors in warm temperatures where heat-related illnesses like heat cramps, heat strokes, heat exhaustion, etc. are possible.