The Original Drinkwell Fountain - now with an extra 50 oz. expander included. The proven product features PetSafe's patented free-falling stream of water system to entice your pet to keep the water well oxygenated and to entice your pet to drink. A charcoal filter helps remove bad tastes and odor - just like in human water purification systems. Adjustable flow control adapts to your pets' needs. Completely disassembles for quick and easy cleaning. Indoor use only.