Whisker City® Water Fountain Filter Cartridges - 4 Pack. Ensure your cat always has access to fresh, great-tasting water with Whisker City® Water Fountain Filter Cartridges, conveniently sold in a 4-pack of Large sized refills. These essential cartridges are designed specifically for various Whisker City fountains, including Pineapple, Ceramic, and Stainless Steel models. Each filter uses Activated Carbon (Charcoal) to effectively remove bad tastes and odors, while the Duo-Density filter pad efficiently captures pet hair and debris, promoting overall pet health and hydration. For best results, replace the cartridge every 2–4 weeks and always rinse the new cartridge thoroughly under cool water before inserting it into the filter chamber.