Product review (5 stars): We have dry clothes again!!
Used this to clean our ridgid aluminum dryer vent that runs about 7 ft. vertical and about 12 ft. horizontal.  I separated the runs at the 90 degree elbow and went to work.  In 20 minutes both runs were as clean as the day I installed them 25 years ago.  You could hardly see through the horizontal run. I figure the air flow was at about 1/2 before cleaning and I was hearing complaints of clothes not getting dry.
All I did was hook up the shop vac outside and went to work from the inside.  No mess what so ever!  Highly recommended!!