Pentek RFFE20-BB # 155263 RFFE-20BB Iron Reduction Big Blue Replacement Water Filter Cartridge Ametek, US Filter, Plymouth, Pentek, Culligan, Kleen Plus, American Plumber, Bruner & Many Other Brands Compatible RFFE20BB Big Blue Radial Flow Iron Reduction Water Filter. 20" long X 4 1/2" diameter. 6 per case, sold individually. Ametek # 155263. The RFFE20-BB cartridge is designed to provide an easy and effective method of reducing iron in water, which greatly improves the taste. This cartridge helps to eliminate the orange and brown stains often found in sinks, toilets, tubs and other plumbing fixtures. It adds no harmful chemicals to the water, making it completely safe for drinking water applications. The RFFE20BB cartridge should be installed on the main cold water line after the pressure tank or water meter. Must be used with a sediment pre-filter, prefilter, pre filter and radial flow GAC carbon post filter. Order a case and save even more.