Product review (4 stars): Good product but throw away the wall adapter.
The only issue with this kit is the wall adapter.  It should fit over the 4 inch duct coming out of your wall and mate to one of the white plastic heads.  But the adapter has an inside diameter of 3-3/4 inches so no way that's going to work.
Be prepared to take a piece of the flex tubing and run it directly from the plastic head to the 4 inch ducting.  To do that you will need to have a couple of duct clamps.