The Micro-Carbon 4 utilizes a standard 12" x 40" mesh washed carbon, which is rated at a nominal 20 micron filter capability. It is designed to remove objectionable tastes and odors, such as those caused by chlorine, hydrogen sulfide ("rotten egg"), iron, etc. One unit will typically last for 5-6 months. Use on ice makers, water fountains, coffee urns and brewers, and other equipment where taste and odor is a concern. Do not use where the water is microbiologically unsafe or with water of unknown quality without adequate disinfection before or after the unit. Tested and Certified by NSF International against ANSI/NSF Standard 42 for Odor and Taste Reduction, Chlorine Reduction, Class I.