RV and Home Brown Stamped Steel Floor Diffuser/Register with Damper 10" X 3" (Duct Opening Size) Outside Dimension 11.5"x 4.5" If your duct opening size

If your duct opening size is 10'' X 10''

The Listed size 10"x 6" is for inside duct opening measurement

Actual outside overall dimensions is 9

The Listed size 12"x12" is for inside duct opening measurement

If you measure outside or surface size

RV and Home Brown Stamped Steel Floor Diffuser/Register with Damper 10" X 3" (Duct Opening Size) Outside Dimension 11.5"x 4.5" If your duct opening sizeThe Listed size 10"x 3" is for inside duct opening (the hole) measurement, actual outside dimension is 11. 5"x 4. 5" Butterfly damper with easy foot operated control dial for desired air flow Two sunk screw holes located at both sides of the register for ceiling and wall mounting with included screws Brown powder coating with matte finish Individually shrink wrapped with card board pad in the back for extra protection