This Kwik-Change four stage reverse osmosis annual replacement filter 4 pack includes one Kwik-Change sediment red label filter, one Kwik-Change carbon block yellow label filter, one Kwik-Change 60 gallon per day reverse osmosis membrane and one Kwik-Change granular activated carbon blue label filter. The sediment filter traps sediment and other particulate matter, such as silt, dirt, and rust which affect the taste and appearance of the water. For best results 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. The 50 gallons per day semi permeable membrane effectively reduces total dissolved solids and sodium as well as a wide range of contaminants such as lead, arsenic, chromium, perchlorate, copper, radium and protozoan cysts, giardia and cryptosporidium. The heart of the reverse osmosis system reduces impurities down to 1/10,000 of a micron.