Product review (5 stars): Works much better than a dryer hose
I just finished installing the Whirlpool 0-18 inch vent periscope.  After I cleaned the lint out of the dryer and the vent pipe in the wall, I adjusted the size of the periscope to fit my dryer to vent connection.  Then, I sealed all of the seams of the periscope so it would not leak air.  I made a one inch cut in the vent pipe in the wall to allow for expansion.  I clamped the periscope onto the back of the dryer and inserted the male connection of the periscope into the vent pipe in the wall.  I tightened up the vent clamps and pushed the washing machine back into place.  Now I get much better airflow to the outside dryer vent and the temperature of the exhaust dryer air is much hotter.  This periscope works great if you remember to seal it with foil vent tape before you install it.