Product review (5 stars): Great solution to lint "arterial sclerosis" in your dryer vent pipe :-).
My dryer seemed like it was taking a looooong time to run the Automatic cycle, and thought it might be a problem with the dryer's moisture sensor, or the vent was getting clogged. I haven't cleaned the 4" solid  duct for my dryer vent in 20 years, so figured that could be part of the problem and start there.

I wasn't sure how flexible the shaft would be to go through the elbows on my dryer's 12' of ductwork, but it handled a 90' turn with no problems. I did take the pipe apart at one elbow to make sure I got all the lint out. The supplied shaft extensions gave me plenty of length to do the job.

Brush could be just a tad bigger to exert more "scrubbing " force to the inside walls of the pipe, but pulling it in and out with my drill running full speed was sufficient to do a good job unsticking all the lint...and it gave me a sort of fun satisfying feeling to really ream the pipe out!

After getting all the lint vacuumed up and the ductwork reassembled, my dryer seems to take a LOT less time to dry a load of clothes :-) . Great, well made product and well worth it.