Product review (5 stars): USE DUCT TAPE TO CONNECT THE SECTIONS!!!
I also used duct tape to connect the brush to the 1st section.  Google says a professional duct cleaning on the dryer costs $90 to $160.  This worked great, what used to take 1.5 hrs to dry, now takes 20 minutes.  The sections are much more "flexible" than I thought they would be, so it worked great going through the multiple bends.  I needed 5 of the 6 sections to get to the outside.  I disconnected the rod from the drill when I reached the outside and then pulled it free and repeated the process again from the inside.  Also, take the time to clean the inside of your dryer vent (inside the dryer) with a vacuum, since you have it away from the wall and have access to it.  Before putting the bird cage protection back on the exterior exhaust vent, run the dryer as it will send loose debris that will clog the bird cage protection.  Ask me how I know??