Pentek RFC-20BB radial flow carbon water filters produce healthier, better-tasting drinking water. The Pentek RFC-20BB water filter provides effective chlorine taste & odor reduction. The Pentek RFC20-BB water filters are constructed with a 25 micron porous polyethylene outer shell and durable polypropylene end caps. The 4-1/2-inch outside diameter cartridge incorporates a spun polypropylene core. Sandwiched between the outer shell and the core is a bed of granular activated carbon (GAC). The unique radial flow design offers the benefits of granular activated carbon (GAC) filtration, such as low pressure drop, while at the same time significantly reducing the release of carbon fines commonly associated with GAC style cartridges.