Product review (5 stars): Way Better Than Plastic! Minor design flaws.
For a few dollars more, buy this well built vent and save yourself the hassle of replacing sun-rotten plastic vents every few years. This unit is sturdy and well made. Only cavet is it really is 4" actually about 4 & 1/32" this makes it VERY difficult to install in a 4" hole in the wall and VERY difficult to slip on 4" dryer vent piping. If this unit was actually 4" or even 3 & 31/32" it would be perfect. Also the lip for nailing the vent to the house is only 1/4" or so, making it very difficult to screw or nail to the house. Still 5 stars for a quality build and well functioning flapper at a good price.