Product review (5 stars): Forget those rigid metal ducts and buy this instead.
So I recently had my dryer repaired, and when we moved it around to fix it, the old metal dryer duct got pretty badly crunched up.  So I went to the local hardware store and bought a new one.  OVER and OVER again the damn thing ripped and eventually popped a hole in the middle.  After cutting my finger on it TWICE and cursing a lot, I threw it out and went looking on Amazon for a dryer duct that looked like it wasn't made out of rigid tin foil.  Well, this was the one I bought.  It was easy to connect to the dryer's exhaust and to the vent leading outside, and it was nice and flexible when I had to move the dryer around.  I didn't need anywhere near the 20' length of it, but when it was delivered it was a compact 18" or so and I only stretched out what I needed to.  Very happy with this product, I'm really happy with it and my wife is getting a little tired of hearing me talk about how great it is.