Review on Hon Guan Booster Efficient Circulation by Anthony Grover

This fan is working as intended. It looks like the airflow in the duct is about twice as high as before. A really nice feature is that even with the fan off, the presence of the fan doesn't completely block airflow through the duct provided by the main fan - it doesn't even block it very much. So you can use this fan purely as a booster - turn it on when you need extra power, turn it off and you'll get the same flow. For a built-in fan, it was very cheap. So far it's great, strong enough and quiet, but I haven't had it that long so who knows how long it will last. If it doesn't break, then 5 stars.