Product review (3 stars): Works, but be aware, either go the distance or blow out the vent, or both!
Ok, so here is the detail on this product.  First, it does what it says it does, but, if you can't go the entire distance (from dryer to vent) this could cause you huge problems.  I have about a 30' run and I bought two kits, adding them together to give me 24'.  I figured I would attack the vent from both ends and it would do a good job.  What happened was I pushed a huge wad of lint in FRONT of the brushes, so when I first came from the outside and then the inside I created a nice air tight lint dam.  When I tested after cleaning ZERO air was leaving the vent.  My brother worked at a chemical plant and he advised me to get an electric blower and blow the vent out.  I did and Man O Man did a wad of stuff come out.  Clearly the brush had loosened everything up, but without blowing it with the blower I could have easily had a fire or ruined the dryer.  So in summary, great product, works as advertised, but you MUST either travel the entire length of the tube or blow it out, or better yet, both!  Good luck, ps photo attached showing what came out AFTER blowing it out.