Catit Fresh & Clear Small Drinking Fountain Provides a re-circulating water flow; Cools, aerates, and eliminates stagnant water Large water-to-surface area adds oxygen to water: for fresher, tastier water Replaceable Purifying Filter: collects food, hair and debris; also helps to reduce bad tastes, odors, and absorbs impurities present in tap water Easy to clean and maintain; Energy-efficient Replacement filters sold separately