Fangrui Product Details Cat Water Fountain Filters: Composed Of High-quality Materials. Effectively To Filter Hair, Heavy Metals , Keeps Water Fresh And Improve The Taste Of The Water Triple Filtration System: Softens Hard Tap Water So That Pets Can Drink Clean And Fresh Water From Cat Fountain, Helps Pet To Increase Water Consumption And Reduce The Risk Of Urinary Tract Infections. Wide Compatibility: Diameter Of Hollow Circle Is About 1.4 Inch, Diameter Of Outer Circle Is About 5 Inch, Compatible With Most 84oz/2.5l Round Cat Fountain/pet Fountains On Market. [keep Your Pet Healthy]each Filter Is Composed Of High-quality Materials. They Can Filter Hair, Heavy Metals, And Improve The Taste Of The Water So That Pets Can Drink Clean And Fresh Water All Day, Which Helps To Increase Water Consumption And Reduce The Risk Of Urinary Tract Infections. Also, Adding A Pre-filter Sponge Around The Pump To Better Filter Impurities And Extend Pump Life. Attention: To Prevent The Activated Carbon Dust From Shedding Into Water, Please Soak