New Versoin: Extra 2 packs of Lon Exchange Resin are added in each replacement filter. With dual-action water softening filter for lon Exchange Resin + Active Carbon, it can filter dirt effectively. Powerful Purify Water: Water quality can be removed by the three 3 types of filtration (Resin, Charcoal, filter cotton fabrics). The external polyester layer on each filter captures hair and debris. Three steps of filtration can assure the quality of the water and enhance the taste for your lovely cat. The filter removes magnesium and calcium from tap water. These minerals can accumulate in your pet's lower urinary tract and lead to urinary tract diseases, which is a common health issue for cats. 8 Pack Supply-- Filter for fountain can last up to 3-4 weeks for one cat to achieve the best quality of water, we suggested to replace it in time.8 Packs of filter give you an 8 month supply. Package included: 8*Cat fountain replacement filters. Compatible with 2.5L cube fountains.