Dual-Action filters: Ion Exchange Resin + Premium Active Carbon. Pack of 4 premium activated carbon filters, size: 5 x 0.4 inch (D x H). Replace filter every 2-4 weeks to maintain water freshness, keep your pets a happy life. Kindly note: Rinse filter with water thoroughly before use. Easy to install and use. Replacement water fountain filters compatible with the flower fountains, catches hair and debris, remove impurities and odor, keep the water tasting fresh. basic