UnderhillNG650-DFH-10 Magnum UltraMAX Premium PRO Series TurboShift 1 Inch High Flow Dual Variable Flow

Q: watched your video. what's the difference in "single variable flow" vs "dual variable flow" ?

The single flow goes through the entire pattern at the same general flow rate. The variable will start going through about half of the pattern at one flow rate, and then click into a higher flow rate where it will go through the entire pattern at that rate.