Product review (3 stars): YMMV...It works but may not be worth the trouble or expen$e
The vent works but was more difficult to install than anticipated and only gained a modest reduction in space between the back of the dryer and the wall.  Unless you have a near perfect setup, you will definitely need a set of tin snips.  Also, to complete the install, you will likely need to use aluminum foil tape to help seal the ends.

Now that I have it installed, I don't believe it was worth the effort or expense. As stated previously the improvement was minor, perhaps 1.5 inches gain.  Also, there is one issue not mentioned that is major:  Because the periscope vent is rigid, once installed, you have essentially locked in the position of the dryer and cannot move it significantly without having to remove the connection to the wall or dryer.  There is no simple pulling the dryer out to retrieve an item or clean behind it.  That alone makes me question the long term usability and value of this product.

Bottom line, I am using it but will likely revert back to the flexible aluminum hose vent eventually. It is a great idea but the actual installation and long term usability make it of limited value unless you have just the right situation.