4 Inch ValuLine Centrifugal Inline Fan Fits 4 inch duct, 171 CFM, 1 amp. Includes attached 120v power cord, mounting brackets and mounting hardware. Fresh, moving air is important to the success of indoor gardening. ValuLine Fans have a fan wheel composed of a number of blades mounted around a hub, which turns on a shaft that passes through the fan housing. Air is rotated 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing.