KDF/Catalytic Carbon Filters reduce iron, sulfur, chlorine, chloramines and heavy metals. Great for city or well water! Bacteriostatic qualities do not allow microbes to breed in filter. Doubles standard green carbon filter. #741622 is 10 in x 2.5 in. #741624 is 20 in x 2.5 in. #741626 is 20 in x 4.5 in.