The Chill-Its 6230 Standard Phase Change Cooling Vest keeps workers cooler, safer and more productive. The phase change cooling material maintains a 64° F (18° C) temperature for up to 4 hours when activated. The vest is made of a comfortable cotton blend fabric with adjustable hook and loop closures at the shoulders and waist to provide a customized comfortable fit. SIZING The cooling vest comes in two sizes ranging from S/M (32in - 40in / 81cm - 102cm) to L/XL (40in - 52in / 102cm - 132cm). To find your size, wrap a tape measure around the widest part of your chest, under your arms, and completely around your torso. See size chart for more information. HOW TO USE 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.