Omnifilter-T08 Radial Flow Carbon Filter - Compatible with Pentek RFC-BB # 155141 / Ametek / US Filter / Plymouth / Kleen Plus / American Plumber / Bruner & Many Other Brands. Radial Flow Big Blue Carbon 25 Micron Water Filter. 10" long X 4 1/2" diameter. 8 per case, sold individually. RFC cartridges are constructed with a porous polypropylene outer shell and durable polypropylene end caps. 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 style cartridges. RFC cartridges are ideal for point-of-entry and other high flow rate applications.