The Chill-Its 6215 Premium Phase Change Cooling Vest is made to house phase change cooling packs to keep 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 modacrylic cotton blend FR fabric which meets ASTMF1506 requirements as well as classified to NFPA (CAT1). The adjustable hook and loop closures at the shoulders and waist provide a customized and 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). HOW TO USE *** Cooling packs 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.