Product review (4 stars): Whirlpool 4396004 Dryer Vent Duct
Allows dryer to be placed closer to wall.  Requires a 4" round hole to be drilled or cut into the floor. Also requires two 1/2" x 1/2" notches cut on opposite sides of floor hole to clear reinforcing wings.  May require a 4" diameter dryer vent pipe extender, depending the length of your dryer's vent pipe (most are flush with the back of the dryer). You will require at least one 4" diameter clamp band (two, if you need a 4" diameter dryer vent pipe extender) to fasten the Whirlpool 4396004 onto the dryer's vent pipe. I recommend metal clamp band(s) because the dryer vent pipe can get pretty hot.  This is made of light-gauge aluminum, but is sturdy enough if you're careful.

DO NOT confuse with Whirlpool 4396005 which has an INSIDE THE DRYER VENT elbow, you want this model 439604 to connect to the OUTSIDE of the dryer vent pipe.