Reverse Osmosis Revolution Whole House 3-Stage Water Filtration System, 3/4" port with 2 valves and extra 3 filters set 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: Premium 10" GAC Granular Activated Carbon filter removes chlorine, radon, VOCs (volatile organic compounds) and other common chemicals. This filter also removes cloudiness, offensive odors, colors and unpleasant tastes. 3rd stage: 10" Premium CTO Carbon Block filter removes chlorine, VOCs (volatile organic compounds, including insecticides, pesticides and industrial solvent). Taste improvement. Build in USA. Connection: 3/4" thread. included 1 extra set of filters as a replacement. You need to change filters every 3 months.