RV and Home Brown Stamped Steel Floor Diffuser/Register with Damper 8" X 4" (Duct Opening Size) Outside Dimension 9.6"x 5.6" Do not measure the surface

Do not measure the surface as registers/vents are measured by inside dimensions

Compliant with ANSI Z21

• Coiled Restraining Cable with mounting hardware for safety

it refers to the size of the "tongue"  so that it will fit in a 8"x8" hole

RV and Home Brown Stamped Steel Floor Diffuser/Register with Damper 8" X 4" (Duct Opening Size) Outside Dimension 9.6"x 5.6" Do not measure the surfaceThe Listed size 8"x 4" is for inside duct opening measurement, actual outside dimension is 9. 6"x 5. 6" 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