Product review (5 stars): This is a perfect replacement. Be aware there are two sizes of ...
This is a perfect replacement.  Be aware there are two sizes of ducting that this will receive, but you have to order the correct size as it is not field adjustable.  Pick the correct one and consider replacing the base if this is a replacement.  If you order the wrong size, the cover is the same and will fit either base if you don't want to change the base.