Our FI-KDF55-20BB filter cartridges have superior taste and odor removal capabilities. There are two types of media in these types of filters: the KDF media in this cartridge specializes in the removal of heavy metals and chlorine and the granular coconut shell activated carbon. KDF process media are high-purity copper-zinc granules - an effective chlorine removal agent used in point-of-entry (POE) treatment of municipal water supplies. This unique, innovative and environmentally responsible media uses redox (the exchange of electrons) to effectively reduce/remove chlorine, iron, hydrogen sulfide, heavy metals in potable water without the use of chemicals. What's more, KDF 55 media is highly efficient and tank size requirements are modest for more economical system engineering and installation.The KDF55 20" filter (4.5"D x 20"L) fits in all 20" standard BB housings.