Uses ordinary tap water. Simply fill, pump and mist. Use over and over again. No batteries required. Pressurized water is forced through a specially designed stainless steel nozzle, atomizing it into a fine mist (1/10 of a hair size). As the mist hits the air it flash evaporates cooling the air dramatically. Try adding ice for an even cooler sensation. Cools for up to 2 hours of intermittent use or 20 minutes of continual mist. 3" diameter x 12" long. 1 lb. Cools air as much as 30?. Great for sports, sun bathing, golfing, exercising, walking, biking, hiking, gardening and any outdoor event. Combining with a 30 pint dehumidifier, the cooler could be used indoor as well.