Product review (4 stars): Good product - buy foil tape to go with it.
As someone else mentioned, purchase some foil tape to go with this.  I would not trust the seal without the tape - I have a gas dryer and didn't want to chance letting fumes escape into my laundry room.

It definitely saved a few inches off using regular 4 inch exhaust  tubing which allowed me to move the dryer a bit closer to the wall.