CompCooler Backpack ICE Water Cooling System (BPIC) is made up of Backpack ICE Water Circulation Unit and Reversible Liquid Cooling Vest. BPIC circulates cold water and continuously flow around your body, keep user cool and comfortable in hot conditions. Backpack ICE Water Circulation Unit includes 3L freezable quick release bladder, 7.4V Mini pump, 2200mAh battery. User may expect long time and extreme cooling feeling from 3L QR bladder, easy to replace and extend cooling time. Mesh liquid cooling vest (Dark Green and Black reversible) provides better air permeability and quick cooling performance, left and right water connection interchangeable. Inlet water filter prevent pump block. 3-6 hours cooling from 3L frozen bladder, 2-4 hours from ICE cubes, 7.4V 2200mAh rechargeable battery provides up to 10 hours operation. Cooling temperature range 36°F-68°F (2°C-20°C), Noise: 48dBA, Vest size: XS/S, M/L, XL/2XL, 3XL/4XL, vest has 15-30% stretch expansion by fabric (10cm/4" Max) and adjustable device (15cm/6" Max) to keep body fit. Ambient 0°C-60°C (32°F-140°F). This model was designed for underwear applications. Features: Extreme Cooling Performance 36°F-68°F, Well-distributed Four Zones Liquid Cooling Channel, Evenly Body Cooling Comfortable Skin Cool Feeling, Soft Stretch Air Permeability Mesh Fabric, Soft Micro Tubing Embedded on the liner, No skin scratch feeling Reversible Liquid Cooling Vest, Body Fit Vest and Underwear Application, Front Zipper and Sides Adjustable Device Provides 15-30% Stretch Expansion 3L Freezable Quick Release Bladder, Quick Body Cooling, Easy to Replace and Extend Cooling Time Safety and Healthy, Clean ICE Water Circulation for Body Cooling, 100% Safe Physical Cooling, Friendly and Environmentally CompCooler Backpack ICE Water Cooling System with 3L Detachable Bladder