The Pentair Pentek EP-20BB is a 20-inch Big Blue whole-house carbon block cartridge that reduces chlorine taste and odor and other unwanted tastes and odors for cleaner, better-tasting water. It is molded from bonded powdered activated carbon (PAC) and rated at a nominal 5 microns, so it also captures fine sediment. A high-porosity design keeps water moving through the block as the carbon works, so more of the carbon is used before the cartridge plugs, all at low pressure drop. A polyolefin outer wrap acts as a pre-filter, trapping sediment that would otherwise plug a carbon block and extending the cartridge's useful life. Measuring 20" x 4.5", it fits all 20-inch Pentair Pentek Big Blue and other heavy-duty housings and is tested and certified by NSF International to NSF/ANSI Standard 42 for material requirements. Each cartridge provides up to 44,000 gallons at a low 2 psi drop at 4 gpm and handles water up to 180°F. Ships as a value 4-pack; replace about every 12 months.