Replacement purifying filters for use with the Dogit Fresh & Clear Large Drinking Fountain. The dual-function filter features foam to collect debris, food, hair and sediment and activated carbon helps reduce bad tastes, odors and absorbs other impurities present in tap water. Replace every 3 weeks or when there are visible signs of the filter saturated with foreign matter. More frequent changes may be necessary due to indoor environmental and water conditions, as well as multiple pet use. Shipping weight: 1/4 lb.