Features: Value pack with 4 filters. Compatible with YOUTH, HOMMI, ISYOUNG, KOALAD, HAPPYPAPA, PEDY, DADYPET, automatic flower fountain and other same size. Size: 5 inch (outer diameter), 1.5 inch (inner diameter). The filter is made of resin and activated carbon to remove chlorine, odor and organic pollutants from the water. To improve the water quality , three types of filtration (resin, charcoal, filter cotton cloth) can be used to remove impurities and debris from the outer polyester layer of each filter. The three steps of filtration can ensure your cat’s quality and improve your cat’s taste. It may take 3-4 weeks to reach standard water quality. We recommend that you change it in time to provide your cat and dog with healthy water and improve water quality. 3-layer filtration system filtration deodorization purification: The first layer of PPF cotton microporous filter hair lining: The second layer of activated carbon is used to remove scale and purify the water quality The