Product review (5 stars): Best thing since indoor plumbing!
The 'plumber' installing my appliances didn't know about these.  He wanted to use stovepipe vent elbows. Leave my drier a foot from the wall.  NO!  I bought this, got it in 2 days and gave it to him to use behind my drier.  Now he thinks they're the best thing since indoor plumbing!  Well made product,  proper sizing makes it easier to install than some others.