Product Details This insulated Hydration Backpack incorporates a high efficiency battery powered pump to supply ice chilled water to the Personal Cooling Vest. Fill with four pounds of ice plus one pint of water for four or more hours of body cooling. The pump can run for eight hours continuously on ten NiMH rechargeable or eight alkaline AA cells in the quick-change Power Pack (included). This backpack is also a hydration pack serving up chilled filtered drinking water on demand. Purchase the Personal Cooling Vest and Hydration Backpack together as a complete Personal Cooling System and save! The complete Personal Cooling System is perfect for sports racing motorcycling bicycling construction and industrial uses providing a personal microclimate of cool in hot and humid environments.