Product review (5 stars): Great, cheap, easy insurance!!!
My review is for why you should use this before waiting too long like me. A worker told me my under-house dryer duct had corrosion on the outside and I should try cleaning possible clog. I ran a snake in from the outside and pulled out a lot of lint. There was  now less air exhaust than before; almost none. Figuring I made the clog worse, I ran snake from the dryer side with no improvement. I then searched Amazon for help and bought this brush. It works quite nicely-but I noticed some sticking after pulling out more debris. So the last resort was me under house to see what's what. The duct was destroyed- see pics. I think it was so corroded that just the snake ruined it for good. Our home is from mid 1970's. We bought it in 1992. So I know since at least '92, it's not been cleaned. It was completely full of debris. Tiny, minute amounts of lint over the years through your dryer filter build up to result in this.  Lesson learned; take 15 minutes to clean the duct every couple years unless you enjoy being under your house. Like me ;(