Pre Filter fan Sponge: The included thick sponge acts as an additional barrier to collect debris and pet hair before reaching the motor, assisting in maintaining your pet fountain ' s motor durability and supporting uninterrupted water circulation Advanced 4 Layer Filtration: Contains dense cotton layer, natural shell carbon and resin components to remove particles, hair, impurities and heavy metals from water, offering multi purification for cleaner drinking water Easy Installation Process: Simply soak new in clean water for 5 minutes and rinse thoroughly before use to minimize carbon particles, protecting your pet water dispenser ' s cleanliness and filtration effectiveness Recommended Replacement Cycle: For optimal results with your pet water fountain, replace both filter and sponge every 2 4 weeks (more frequently for multiple pets) to maintain a constant supply of purified water Wide Compatibility: This replacement filter set with fan sponge is designed to fit WF120 12L large stainless steel pet water fountain, providing proper installation and consistent action for your pet water dispenser