12"x 6" (Duct Opening Size) 2-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 13.75" X 7.75" Difference between "inside" and "outside":

Difference between "inside" and "outside": Inside (duct opening) is the measurement you can see after taking the vent off the wall or ceiling

The Listed size 12"x20" is for inside duct opening measurement

Individually shrink wrapped with card board pad in the back for extra protection

The listed size 12" x 10" is for the inside duct opening measurement

12"x 6" (Duct Opening Size) 2-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 13.75" X 7.75" Difference between "inside" and "outside":First thing to know about size selection: take the vent cover off the wall or ceiling. Measure the duct opening where the vent can fit in. Use the measurement to determine right size to buy. This product has listed size 12w X 6h is for duct opening measurement only, actual outsize overall dimensions is 13. 75 wide by 7. 75 high. If your duct opening size is 12 x 6, this is the right size and will fit in well. If you measure outside or surface size,