The AlphaCool 5V Circulatory Cooling Vest's built-in water circulation unit brings the highest quality cooling technology into a compact vest for better wearability and easy operation. It comes with 4 refillable ice packs, each providing 1-3 hours of cooling. The rechargeable battery provides up to 8 hours of liquid cooling through tubing embedded in a mesh liner. The mini pump circulates cold water that continuously flows throughout the vest, keeping it cool and comfortable in hot conditions.