Product review (1 stars): Not for recirculated air
Looks good, a pain to install, instructions suck, support sucks. The "telescoping duct" is not really telescoping and it's horrible, with sharp edges that will cut you.

Most importantly, though, this is definitely not for recycling air back into the room, even with filters. The flow of air it takes in is _much_ higher than the outlet hole at the top can pass through, so the air tries to escape through all other possible openings, too. Specifically, between the duct and the wall, into the electrical outlet and so on. I'm guessing condensation inside on the metal surface of the duct is going to become an issue, too.

Horrible design and a horrible implementation, stay away.