Product review (5 stars): Works great, but follow INSTRUCTIONS as most people will not do.
Make sure you follow the directions and this will clean out the lines.  Mine is 20ft long and it clean it out, but you go back and forth to clean till no more stuff comes out.  My vent goes up thru to the roof and vents so it was easy for stuff to fall,  The dryer itself and the flex hose was really bad and it cleaned them out with no issue.  I did use a shop vac and cleaned again to get anything left from the first attempt.  I am attaching before and after photos to show how clean this device is.  It does flex very well and make sure you follow the instructions when using a drill motor.  In fact my brother-in-law has got it now.  LOL