Protect your whole home with cleaner, safer, better tasting water using the Pentair OMNIFilter PB55-20 premium carbon block replacement cartridge. Installed at your main water line, it reduces lead and cysts such as Cryptosporidium and Giardia along with chlorine taste and odor, so the water at every tap is cleaner and tastes better. The PB55-20 is a dense 0.5 micron carbon block built for serious filtration. It is third party NSF and ANSI Standard 53 certified to reduce lead and cysts at 10 gpm and 40,000 gallon capacity when used in the Pentair OMNIFilter BF55 filter housing or PB55 filtration system. The carbon block design delivers a high flow rate with low pressure drop, so you get strong filtration without sacrificing water pressure. This 20 inch by 4.5 inch heavy duty big blue cartridge also fits 20 inch by 4.5 inch heavy duty housings from other major brands and can replace most carbon block cartridges of the same size. Plan on a fresh cartridge every 4 to 5 months, or sooner if you notice reduced water pressure or a change in water quality.