Product review (1 stars): poor construction abounds
Don't even think about buying this product
First, it is made from the lightest gauge aluminum with exception of the 90 elbow. Second, poor construction abounds. There are up to 1/4" gaps in the junction between the main body and round duct adapter. This adapter is pop riveted together with slightly heavier gauge metal, some of which appears to have been hacksawed to make it fit. There are visible gaps in the corners. It will leak and blow dryer dust unless you seal the gaps. The coupling collar  attaching to the dryer is too short to clamp properly. A much heavier gauge, better product is available from Everbilt at Home Depot. I didn't install this procuct