Product review (3 stars): look before you buy
before you buy this product, make sure you check your outside vent first.  i bought this first and then went on the roof and lo and behold, the vent was shaped like the upper half of the letter "s" with such a sharp turn, that the product could not make that sharp a turn. so i cleaned the vent from the bottom to the top. i guess it worked o. k. that way.