Perfect Fit: Our pet water filter is 3.5cm inner diameter and 12.5cm outer diameter, compatible with most 2.4L round pet fountains on the market. (Please check carefully the filter size you need before purchasing). Triple Filtration System: The cat water fountain replacement filter is made of a layer of non-woven fabric, coconut shell activated carbon and ion exchange resin, which can effectively filter hair, residue and heavy metals, remove odor, soften water and achieve better water taste. Keep the fountain water fresher. Keep your pet healthy: Cat water filters help improve the taste of water and allow pets to drink clean, fresh water throughout the day, which helps increase water consumption and reduce the risk of urinary tract infections. Easy to use: Rinse the cat carbon filter thoroughly with water before use to remove carbon dust and activate the resin! When installing, place the flat side up to ensure optimal filtration. For the health of your beloved pet, we recommend