The Pentair Pentek GAC-20 is a 20-inch granular activated carbon (GAC) cartridge that reduces chlorine taste and odor and other unwanted tastes and odors to give you cleaner, better-tasting drinking water. It is built to allow maximum contact between the water and the carbon for effective adsorption. Water enters one end of the cartridge and passes through the entire length of the carbon bed before exiting the other end. An internal expansion pad minimizes channeling or bypass, and a spun polypropylene post-filter reduces carbon fines and other suspended particles from the filtered water. The cartridge uses granular activated carbon media in a polystyrene outer casing with polystyrene end caps and is rated for water from 40 to 125 degrees F. This 2.88" x 20" cartridge fits standard 20-inch filter housings and replaces any 20" x 2.5" carbon filter cartridge. It provides chlorine taste and odor reduction for up to 10,000 gallons at 2.0 gpm. Replace the cartridge when you notice a drop in water pressure or water quality.