TFT's SHO-FLOW 2 HIGH FLOW BLUETOOTH® generates its own power using an unobstructed water driven turbine, with a built in stream straightener, that will pass debris up to 1.7" (43 mm) in diameter. Starting at 500 GPM (2000 l/min), the turbine generates power needed to supply a BLUETOOTH® connection to any smart device. Choose units you want displayed from your smart device; gpm, gps, l/min or l/sec. Full flow range 500 - 1250 gpm (8.3 - 20.8 gps) (2000 - 5000 l/min) (31.6 - 75 l/sec)