Product review (5 stars): Be ready to share it with the neighborhood
Our 20 year old house wasn't maintained well by the previous owner so I should have assumed when my dryer was taking long to dry the duct needed a good cleaning.  Our duct is a poor design that runs from the basement up 2.5 stories.  This worked like a charm, with a little ingenuity.

We started at the bottom of the duct cleaning out the bottom half  and then climbed on the roof and threaded it from the top and then shoved a 30' garden hose, just the hose without water,  from top to bottom to catch anything in the middle we couldn't reach (most ducts are 1/3 of this length).  We ended up with a 5-gallon bucket of lint and a sense of wonder of how our house didn't burn to the ground!  My drying time went from 90 minutes a load to 35 minutes a load.

After telling our neighbors of our Friday night highlight they all borrowed it with similar results.