Compatible with our 108oz/3.2L Stainless Steel Water Level Window Cat Water Fountain. Pet water fountain need to replace the carbon filter every 1-2 weeks.(The hot weather breeds mosquitoes, please replace the carbon filter every weeks, and replace the foam filter every two months to keep the water fresh. Set of 3 filters and 3 sponges compatible, easy replacement, bringing more protection to your pet. First Filter, Block Hair and Debris. Middle Filter, Remove Residual Heavy Metals. Third Filter, Healthier, High-quality Flowing Water. Allow pets to drink clean, fresh water throughout the day. Soak the filter in a clean bowl for 5 minutes. Notes,The filter must be fully soaked before the fountain is turned on; Otherwise, the water may not diuse through the lter and cause overow. Do not soak the lter in the fountain tank to avoid dust on the surface. NOTE: For your pet's health and fountain's safety, please buy the official filters from on .