Product review (5 stars): Years of gunk gone
I waited far too long to get and use this.  When put to use, it was surprising just how much gunk had built up in the duct.  This kit was the answer.  Hooked up to battery powered drill this kit removed a ton of gunk.  The extensions flexed to make it around the corners with no problems.  A shop vacuum works well to suck or blow the residual debris out of the duct.  Now my dryer duct is clean as a whistle.