Product review (1 stars): Good design idea, terrible implementation.
In my opinion this duct, as sold, is absolutely useless piece of junk. The duct's bottom collar is too short to be attached to the dryer's exhaust line. If this duct has to be attached in a vertical position (most likely intended configuration), it's stem stays flat on the back bulge of the dryer's cabinet (at drum's location) and the collar is too far from the dryer's exhaust to be connected.  A longer duct's connection collar, either manufactured or supplied as an optional/adjustable part could make this device usable.