The Drinkwell® 360 pre-filter traps any large particles, hair, and debris in the water before they reach the pump, providing better overall filtration and cleaner water for your pet. These foam filters help keep the pump cleaner in between cleanings and maintain the fountain's flow rate. These filters are compatible with the Drinkwell® 360 Plastic Fountain. They're not compatible with the Drinkwell® 360 Stainless Steel Fountain.