Product review (5 stars): Works well
I used this product today to clean my dryer duct (about 13 feet with several elbows). I was surprised by how much lint came out - about half a grocery bag worth. It was compacted so it is unlikely that it would ever have blown out on its own.  This was a quick and painless process. While you're at it, you should also open up your dryer and vacuum it out. I recommend this product.