Drinkwell Original Pet Fountain uses an innovative watering system featuring a free-falling stream of water. A large charcoal filter removes bad tastes and odors giving your pet the best possible and most appealing way to stay hydrated. By using a 5-inch falling stream of water， the Pet Fountain continually aerates your pet's water with healthful oxygen. Simple， safe and proven to benefit your pet's health， the Drinkwell Pet Fountain is a great way to show your pets just how much you care. Comes with 1 charcoal filter.