55W UV Ultraviolet + Sediment & CTO Carbon Well Water Filter/Sterilizer System Replacement filter package for this system is Amazon item B0110LUKR0 1st Stage: 20 Micron Sediment Filter. For particles such as sand, dirt, silt, and rust. To remove these particles it allows a better performance for the following Carbon Block filter. 2nd Stage: 5 Micron Carbon Block Filter. Removes chlorine, bad taste and odor, organic solvents and organic chemicals that contribute to bad taste and odor. 3rd Stage: 1 Micron Sediment Filter. For particles such as sand, dirt, silt, and rust down to 1 micron 4th Stage: Powerful 55W 12 GPM Ultra Violet Light Sterilizer Kills harmful Bacteria, E Coli, Viruses Fungi, Algae most microorganisms including cryptosporidium and giardia, and many other contaminants.