Used in combination with Activated Carbon, KDF can significantly extend the life of filter cartridges. KDF is an oxidation-reduction (redox) media that removes chlorine, hydrogen sulfide and many other contaminants. KDF is available in several varieties for specific applications. KDF-55 is removes chlorine and reduces heavy metals. KDF-85 removes hydrogen sulfide and reduces iron. Both KDF redox medias are bacteriostatic and control the growth of microorganisms in filters. KDF allows Activated Carbon to do a better job at removing taste and odor. Model: AF-20-2012 Dimensions:20" x 2.5" Flow Rate (GPM) / Operiatng:1 / Maximum:52 Capacity (gal) :22,000