The Flowmaster measures how much filtered water that has gone through the system and alerts you when it's time to change filters. You can program in the filter capacity and when you reach the target number of gallons, the Flowmaster beeps. No more guessing when your filters are past their useful life. Ensures your system at its peak efficiency for removing contaminants. High flow model ranges from 0.2 GPM to 2.0 GPM flow rate and comes with 3/8" quick connect fittings for Evolution RO1000, Merlin-Garden Pro and Tall Boy (use 2 pieces of #728907 to convert for use with Small Boy).