Cat Fountain Replacement Filter. Keep your cat’s drinking water fresh and clean. Help you take care of your cat’s health. Most of the filters on the market are made from activated carbon. But these filters are made of high quality activated carbon resin and cotton mesh. The water is deeply purified and safer. features: value pack of 12 filters. compale with Youthink Hommi Isyoung Koalad Happypapa Pedy and others of the same size. Size: 5 (outer diameter) 1.5 (inner diameter) Double action filters: resin and activated carbon. The resin can soften the water and reduce the risk of stones.