The Brondell H2O+ Pearl Carbon Block replacement filter (HF-25) utilizes advanced carbon block technology and a patented inner core filter. Replacement is a breeze - simply twist the base and this filter installs quickly into the H2O+ Pearl system. After replacing the filter, flush with water for 5 minutes to activate and dramatically reduce industrial chemicals, particulates, volatile organic compounds (VOC's), and bad tastes and odors. Reduce harmful chemicals like Atrazine, Chlorobenzene, Trihalomethanes, Methoxychlor, Endrin, 2,4-D, Benzine, DBCP and Aesthetic Chlorine from your tap water for a healthier home and family. Choose Brondell H2O+ for better water.