Simply put, this inline duct fan seems to be as good as any of the competing brands, and makes one wonder why the others cost so much more. The only issue I had was a loud high-pitched whine that came from the controller box even when the fan was completely off. (Since the controller monitors temperature and humidity, it's never really \"off.\") Then I got around to plugging in the temperature sensor cable (which not all competitors provide or support), and the whine disappeared completely. I guess some circuitry was switching on and off to check temperature, and with no sensor it made an audible switching sound. In any case, this is a flexible controller and a fully functional fan, and I can't find any fault with it. And it has an anti-back-flow feature so outside air doesn't blow back into the duct when the fan is off. Mine is installed on the high-pressure side of the shop, and there's almost always prevailing wind against that side of the building, but no indication of any draft back through the fan. This can be very important, not only to prevent heat loss, but also to prevent possibly toxic dust and particulates that accumulate in the duct from being blown back inside. I will definitely pay attention to other products from Vevor.
Tim Counts 
