【 Flexible control speed】Powerful blower with a external fan speed controller. You can choose any speed from 0 to 100% using the included variable speed controller without creating background noise or hum at low speeds. 【Parameters 】DUCT DIAMETER: 6”(150mm) — Airflow: 402 CFM —Power 55W —Noise: 32 dBA —Pressure: 502 Pa—IP44 Rating 【Quiet and energy 】Saving performance is very good: EC motors with mixed flow design and PWM control can use precise electronic pulses. This allows the embedded fan to run more quietly and reach low speeds without generating noise or heat. The energy efficiency of EC motors is also twice as high, and can save up to 40% of energy costs, and can recover costs in the long run. 【Wide applications 】This Inline Duct Fan are used in indoor grow facilities and vertical farms, heating and cooling transfer, commercial drying and air filtration applications. Our inline blowers can also create negative pressure environments, simulate wind, exhaust odors and smoke as well as intake fresh air from outdoors 【Guarantee】100% refund or free replacement if quality issue happened during one year. Please feel free to contact us for any technology issue or other comments. We answer in 24 hours.