Gallonage and filter capacity monitor operates at flow rates between 0.01?0.1 GPM. Ultra low flow model. Accurately tracks the number of gallons of filtered water produced and alerts you when it?s time to change your filters. Also shows real-time flow rates. Displays in gallons or liters. For use with Stealth RO, Triton RO or any other systems with 1/4 in fittings and flow rates up to 1/2 GPM.