This Kwik-Change UF3 and 4 stage reverse osmosis semi-annual replacement filter 2 pack includes one Kwik-Change sediment red label filter and one Kwik-Change carbon block yellow label filter. The sediment filter traps sediment and other particulate matter, such as dirt, silt and rust which affect the taste and appearance of the water. The 5 Micron filtration rating is in the particle filtration category and is equivalent in size to milled flour. This filter is designed to be changed out every 6 months or every 1,350 gallons. The five micron carbon block filter reduces chlorine, objectionable tastes and odors.