I have the unit described below from filter direct:
RD-106, AQUARIUM REEF & HOME DRINKING 2 OUTPUTS Reverse Osmosis RO + DI SYSTEM
Overall rejection/removal rate: 98% to 99% for the Ultra-pure, 95% for the drinking water
1st stage: 5 micron sediment filter, removes sediment, rust, dirt. (replace every 6-12 month)
2nd & 3rd stage: premium grade coconut shell carbon block filter, removes chlorine, chloramines, bad taste and odor (replace every 6-12 month)
4th stage high rejection TFC-100GPD membrane, removes 95% to 98% of chemical, minerals, dissolved solids, like arsenic, lead, silica, nitrate, copper, ammonia, sodium, fluoride, etc. (replace every 12-36 month)
5th & 6th stage: de-ionized filter, further removes the mineral and chemical contents of water and achieving 99% to 100% removal rate (replace as needed, or after 600 to 1000 gallons). It comes with refillable clear casing. The DI resin inside changes color from green to dark brown when the resin is exhausted.