Product review (4 stars): Vent Periscope
Our washer and dryer are along one wall in the kitchen, so we need to get them as close to the wall as possible.  The existing dryer vent did not line up with that on the dryer, so initially we used a flexible 4" aluminum connector, which meant that the back of the dryer was more than 4" from the wall.  We thought of aligning the vent inlet and outlet, but that would have involved cutting a new 4" hole through a concrete block wall, and we did not have any power equipment with which to do this task and did not wish to do it by hand with a 12" star drill and a hammer.  The Whirlpool Vent Periscope allowed us to close the gap to about 2".  Installation involved the use of tin snips to shorten the degree to which the pipe from the external vent came into the room and to shape the Whirlpool Vent Periscope to the proper length.  The sides, ends, and area around the vent inlet and outlet of the Periscope were then wrapped twice in aluminum tape to prevent lint from being released into the kitchen. The Periscope was then easily installed and clamped onto the inlet and outlet.  If you have the tools and are prepared to do the work, you can have an excellent vent pipe that lowers the gap between your dryer and the wall.