Product review (5 stars): Just installed this and it works great
If your dryer is not drying clothes quite like it used to, chances are good that your dryer vent hose is clogged - or at least partially clogged.  Mine was, so I replaced the entire hose and vent hood assembly using this dryer vent hood.  I actually bought a galvanized and this white plastic one because I just wasn't sure how either of them would fit in my wall.

As it turned out, this one fit perfectly.  The galvanized one would have worked too, but I ended up liking the way the white plastic looked outside my house.

The flapper works nicely, theoretically keeping wind and uninvited critters out of the house.

But best of all, my dryer really works now.  The new vent and hose brought it back to full strength!  I read while I was researching these vents/hoses that if the hose is even partially clogged it will cause the dryer to cycle on and off perhaps hundreds of times during one drying session... which - of course - is probably not too good for the switch and certainly not good for getting the dryer to dry timely.

If you haven't done it for a while, and your drying isn't quite up to snuff, change the hose out.  I changed the vent too and I recommend it because if the hose is clogged, chances are the vent hood pipe is clogged too.  It's easy, it works!