The Pentair Pentek GAC-20BB delivers reliable granular activated carbon filtration for whole-house and commercial systems equipped with Big Blue 20-inch housings. Each cartridge reduces chlorine, taste, and odor using a proven GAC media bed, providing cleaner water at a steady flow rate with only 10 psi of pressure drop at 4 gpm.Engineered for consistent performance, the GAC-20BB features an internal polypropylene expansion pad that minimizes channeling and bypass, ensuring water passes evenly through the carbon bed. A spun polypropylene post-filter captures carbon fines before they reach your tap. Polystyrene end caps and outer casing provide structural integrity, while Buna-N and Santoprene gaskets ensure a secure, leak-free seal.Each cartridge is NSF/ANSI Standard 42 certified for material requirements and delivers up to 25,000 gallons of chlorine reduction capacity at 4 gpm. This 4-pack provides extended coverage for households and facilities that depend on dependable water filtration year-round.