Product review (5 stars): Perfect solution for installing dryer in a laundry closet cramped on 3 sides.
The perfect solution to getting the dryer as close to the wall as possible without crushing the flexible duct when the wall connection was offset a foot to the side from the dryer outlet.  I bought two of these and placed one on the dryer and one on the wall outlet.  Four worm drive 4.5" clamps were used.  Heavy duty aluminum flex duct was placed between them.  These elbows easily turn after the clamps are tightened.  Each was pointed upwards at about a 45 degree angle and the duct installed in a loop, not straight between the two, because there was no room  to reach the clamps from the sides of the dryer. We installed one elbow with flex duct on it to the wall outlet first, then next installed the other elbow onto the back of the dryer before we slid it into the closet. The "trick" was figuring out how to get the other end of the flex duct attached to the dryer elbow.  Fortunately, we had a skinny workman who could literally climb over the back of the dryer after tightening the final clamp in order to get out of the tiny laundry closet.  The outside of the wall elbow was only 5.5" from the wall after the installation, which allowed just enough space to get the clamp on.  The back of the dryer was 18" from the wall until the final clamp was tightened, but the loop in the flex duct allowed us to push the dryer to 5;5" from the wall after the workman was out.  Because these elbows are quite a bit stronger than using just flex duct, we are sure the tenant will not crush the dryer hose by attempting to push the dryer closer to the wall, which was our main concern with this installation.  Using these smooth elbows gave minimal resistance to airflow, as observed by looking a the exhaust hood flap that was all the way open. An expensive solution to a simple problem, but one that will allow access to the back of the dryer for future maintenance, while assuring the duct does not get crushed..