Air Blowing Ventilator 1.plastic housing, 2.top quality, low price 3.noiseless and power saving, 4.easy install, promt ship Air Blowing Ventilator 1. Features Circular duct fan is a product which bears many national inventions.It's a new type of duct fan with a patented shape. The size of air inlet is the same as air outlet. The fan can be connected with all kinds of air ducts (the size of air ...