HVAC Plenum Ceiling Box 12X12X10 (12"X12" Square to 10" Round) with Drywall Flange - Connects to Vent Register Diffuser, Galvanized Steel Metal C-Box Duct, Airflow Conditioning Ceiling Registers

Perfect fit

It is exactly what was ordered. Arrived undamaged.

This is 12" if you're measuring the mounting fins or internal box dimensions. The external box dimensions are 12.25"x12.25". That didn't make a difference for my needs, but it could be enough if you're expecting precision. What matters here is that the box is sturdy, and the duct mounting diameter is a perfect 8". What I didn't like is that the box with the fins is indeed too wide to fit between 16" studs if you already drywall up, so this is aimed more for new construction I think. I got around this by bending the vertical fins back. There's enough support from the horizontal supports that it's not going to move.Oh and the edges aren't sharp! That's a good thing. I expected this to cut me if I weren't careful, but I had no trouble.

This is a well made diffuser and even though I ended up not using it because the space was too tight in my attic the seller stepped up and refunded my money. The expense of returning it was greater than the cost of the item but the seller was concerned that I was a satisfied customer and refunded the cost anyway. To me that says a lot and I would buy from him again. Also the quality is higher than what you find at your Home Depot which really sells junk when it comes to vent boxes and such.

Purchasd 4, not easy to cut and install in tight space. Destroyed 2 and garbaged them. Returned 2

Exactly what I needed. The back side of my wall was unfinished though, and this does stick past the stud slightly. I'd recommend the fabricator adjust their design so the depth would work in typical wall construction

Insulated very well. I put this above my wood stove and a insulated duct work with all the fixings. Works wonderfully! To put it between joist I simply made a wood box that it sits on on 2 side only and put few screws in to hold it to joists. Been 3 months no problems expect the coldest bedroom and furthest from the wood stove is hot! Timer switch fixed that problem quick!It is a little flimsy but a few sheet metal screw reinforced it quick.

Incredible deal incredible price. Searched around the city to try to buy in person. No luck. They sit perfectly and works as advertised.