Chill-Its 6250 Lightweight Phase Change Cooling Packs, 6 x 13, 4/PackThe Chill Its Lightweight Phase Change Cooling Vest Packs are made to be inserted into model 6255 Lightweight Phase Change Cooling Vest (sold separately) to keep workers cooler, safer and more productive. The phase change cooling material in the packs is 100% biodegradable and maintain a 64 F (18 C) temperature for up to two hours when activated. These packs are designed to be 30% to 60% lighter weight than other cooling vests on the market. Simply