Universal 10" Reverse Osmosis RO Replacement Set of 4 Filters 1st stage: Premium Quick-Connect 5 micron sediment filter. Dust, dirt, silt, sand, rust and scale particles are trapped here in a filter which also extends the life of the system. 2nd stage: 10" GAC Granulated Activated Carbon Filter. Removes chlorine, chloramine, VOCs and etc. 3rd stage: 10" Premium CTO Carbon Block filter removes chlorine, VOCs (volatile organic compounds, including insecticides, pesticides and industrial solvent). Taste improvement. Made in USA. Last stage: inline post filter GAC T33, 10" x 2"