Watts (MAXETW-FF20) 20"x4.5" C-MAX Carbon Block Chlorine Reduction 5 Micron FilterWatts Premium Filtration MAXETW FF20 20"x4. 5" C MAX Carbon Block Filter High capacity carbon block filtration for chlorine, taste, and odor reduction in whole house and commercial applications. 5 micron nominal rating removes sediment while maintaining flow. 5 Micron Nominal 20,000 Gallon Capacity Bituminous Carbon WHY IT WORKS Engineered for demanding chlorine reduction Solid Carbon Block Made from bituminous carbon with no release of carbon fines.