Fluoride removal filter for use in Doulton DUO dual or triple stage system as well as similar dual countertop systems that use 10 inch cartridges. Reduce unwanted naturally occurring or added fluoride in your drinking water. Cartridge is commonly installedin the first or second (not last) chamber of the DUO drinking water filter. Designed to reduce Fluoride. Length: 10". Filter life: 3 months.