Product review (1 stars): flimsy
The product has potential but it is too flimsy in excution.  The lightweight plastic separated along the elbow seam as I installed a 4" aluminum dryer vent extension.  The extension was itself lightweight.  Very disappointing.  Now I suspect the product wouldn't stand up to normal usage.  It's lightweight material may become soft with heat and it will not stand the impact of accidental household usage, soccer balls, bumps from ladders, kid's playing - that type of thing.  Together with shipping charges, this is something to avoid.