Review on Builders Best 10151 Close Elbow: Optimize Airflow Efficiency in Tight Spaces by Mike Larkin

No holes in fastener for easy attachment to drywall, no flange wide enough to drill your own holes unless the hole in the wall is large enough to slip elbows in. The larger hole and flange cannot reach the drywall to attach the flange. EDIT: I had to put something up to hold it against the wall so it wouldn't blow off the wall and blow out all the hot air and lint that got in through the screen inside the house.