【Multi-Layer Filtration System & Automatic Circulation】This cat water fountain adopts multi-layer composite filtration technology. The impurity filter removes pet hair and dust. The activated carbon cartridge adsorbs impurities, and the ion exchange resin softens the water, effectively reducing limescale and odors. Furthermore, the automatic circulating pet water dispenser keeps the water fresh and delicious at all times, providing safe and beneficial drinking water for pets. (Note: This product comes with 2 filter cartridges.)