Economically priced drop-in cartridge provides quick and easy filter change Dual purpose cartridge for chlorine and sediment filtration High dirt-holding capacity Recommended for chlorinated water supplies The C1 cartridges offer an economical solution for all of your general-purpose water filtration needs. The combination of quality chlorine and sediment filtration makes the PENTEK-C1 an excellent choice for polishing filters for RO systems and a wide range of residential applications.