KDF/Catalytic Carbon Filters reduces 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 x 2.5 inches. #741624 is 20 x 2.5 inches. #741626 is 20 x 4.5 inches.