VIVOSUN Inline Pipe Fan 200 mm Extractor Fan 1257 m³/h with Continuous Speed Controller for Grow Tents, Indoor Garden VentilationEnergy Efficient Ventilation: This blower with a fan speed of 2450 RPM creates an air flow of 740 CFM; It combines the features of both axial and centrifugal fans to achieve optimal ventilation Quiet Operation: The sturdy leather can reduce sound or vibration; Tight and precise construction eliminates rattling; The centrifugal impeller provides powerful airflow and has a low noise of 53 dB Adjustable Speed: This centrifugal fan is equipped with a