Product review (4 stars): could be better
I'm an engineer and many people don't understand what cfm rating means and how to measure it.  U can't put put a piece of paper against the filter as a comparison.  I can't verify that It's truly 900 cfm, but I don't have rust problems either.  Coming out of china, quality control of material for the filters could be different as mine are washed in the dishwasher and we have no rust problem.  Sometimes the control panel is sluggish to respond but it works.  900 cfm may not be obtained if your existing ducting is 6 inches, there is long run and impedes flow.  For 300 bucks, I wouldn't complain since the hood and filters are made of thick stainless.  The fans are quiet and I
don't have any vibration problems.  I guess I am lucky to have good unit.  Cfm is a measure of volume of air per minute, it is not a measure of negative pressure.  The use of filters vs baffles is why placing a piece of paper in front of the unit is not a correct way to measure cfm.