The Ruffwear Swamp Cooler uses natural evaporative cooling to keep your dog cool. Soak it in cold water, wring it out, and fasten around your dog. Evaporative cooling exchanges the dog's heat as water evaporates from the coat's reservoir. The Swamp Cooler's light color is designed to reflect heat from the sun. Combined with the evaporative cooling effect, the Swamp Cooler keeps dogs comfortable when temperatures rise. Auto-lock buckles on each side of the jacket provide easy on/off.