Product review (5 stars): Whirlpool's periscope vent is terrific
This is a terrific device to solve cramped dryer venting problems.  My recommendation is to take your time in measuring and cutting the periscope to the proper size.  The metal is very flimsy, so be careful not to create a bend or fold that changes the shape.  I would also recommend using a high quality metal duct tape to seal all the joints once the final dimensions are determined.  Once installed, this provided a much less obstructed passage for our Maytag dryer exhaust than the circuitous flex hose with all of its bends.