Product review (5 stars): Great product & easy to use
After reading some of the lower rated reviews I was concerned that the product might be fragile or easily damaged.  But, the parts are actually very well made.  The instructions are very detailed and I was careful to follow them to avoid any broken rods or brushes.  My dryer ductwork enters the wall on the second floor, immediately turns 90 degrees straight up, and exits at the the roof vent.  I moved the dryer out of the way and cleaned the duct from inside the house.  I used the vacuum adapter and it worked well.  The 90 degree bend was no problem.  I think the trick is to keep the speed slow, and with your drill clutch adjusted to prevent any overtorque in case the brush or rod gets stuck.  The instructions are clear about this.  I had no sticking problems.  I ran the drill at about 200 rpm and worked the rod into the duct slowly.  It probably took me 10 minutes to clean the entire 11-1/2" duct, including stopping to connect each rod.  Great product.