It is an adjustable filtration media that includes a five stage process for eliminating scale, dirt and fine particulates, odors/off flavors. I believe that for the money and simplicity it's the best system out there.
The Claris uses a Hydrogen (H+) ion exchange rather than a Sodium (Na+)exchange.
"The Claris resin is loaded with hydrogen (H+). The hydrogen ions dissolve the carbonates (CO32- and HCO32-) , and the resin then removes the calcium and magnesium ions (Ca2+ and Mg2+). This process also lowers the pH."
I will soon find out how it tastes.