The PETLIBRO PLWF003 Replacement Filters help to remove hair and heavy metals, improving the taste of water so your furbaby can drink clean, fresh water all day. That better-tasting water can encourage your best friend to drink more, helping to reduce the risk of urinary tract infections. These filters feature a cotton layer, activated carbon and an ion exchange resin to maximize their effectiveness. They are compatible with the PETLIBRO stainless steel cat water fountain PLWF003 (sold separately).