Product review (1 stars): Hard to install in existing wall
Warning...the box is designed for installation before the sheetrock goes on.  No instructions are provided to install it in an existing wall.  I had to heavily modify the box - I cut off the install tabs and enlarged the box's tube hole to get it on the hard metal vent coming down the wall.  Plus it was very difficult to cut the metal vent inside the 3 1/2" wide wall without damaging the sheetrock.  For all the trouble I only eliminated one 90 degree turn, so not sure the box was worth it.  Suggest using a box truly designed for aftermarket use with better install instructions.