Pentek RFC-20 # 155065 RFC20 Radial Flow GAC Carbon Whole House Replacement Water Filter Cartridge Compatible With Culligan, Ametek, US Filter, Plymouth, Kleen Plus, American Plumber, Bruner and Many Other Brands. Radial Flow Granular Activated Carbon Water Filter. 25 micron outer shell. 20" long X 2 7/8" diameter. 6 per case, sold individually. Ametek # 155065. RFC Series cartridges are constructed with a porous polypropylene outer shell and durable polypropylene end caps. 70 micron outer shell. Sandwiched between the outer shell and the core is a bed of granular activated carbon. The unique radial flow design offers the benefit of granular activated carbon filtration, such as low pressure drop, while at the same time eliminating the release of carbon fines commonly associated with GAC carbon style cartridges. RFC Series cartridges are ideal for point-of-entry POE and other high flow rate applications. Order a case and save even more.