10 Inches X 10 Inches is the actual size of the square portion. Your diffuser or register will be slightly larger than this.
Our C-Boxes are built with a 1/2" flange all the way around the square portion which can be used for attachment or folded over.
We also have a full line of ceiling registers and hvac fittings.
The best way to regulate air flow is to install a manual volume damper in the duct run.
Call us with your hole size and duct size so we can help (866) 309-9899
Connects a 8" Round Duct to a 10 x 10 Diffuser or Register Vent.