From the Manufacturer Air king's in-line fan kit series is designed for long life and dependable performance, utilizing an external rotor motorized impeller that gives you the knowledge that the fan will provide years of worry-free ventilation while the plastic housing will not rust or corrode. In-line fans take the noise away from the room and because the fan is remotely mounted, often in an attic, the sound generated from the fan is minimized, allowing for a peaceful and quiet room. In-line fans provide an excellent way to properly ventilate a home with multiple rooms in need of ventilation. With an in-line system, you only need to install one fan instead of multiple room level fans. It is pre-wired for simple and quick installation. Also able to be used with a variable speed control, and is UL approved for wet locations for both residential and commercial applications and rated for continuous use. The aik4x model is an energy star rated unit with 19 power-Watt. It provides 100-CFM of ventilation and provides exhaust capacity for a room of approximately 100-Square-Feet. It utilizes a 4-Inch exhaust duct and includes a 4-Inch round room inlet grill and collar. Housing size: 9-1/2-Inch diameter-by-9-3/8-Inch high.