10"x 4" (Duct Opening Size) 1-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 11.75" X 5.75" Measure the size of the

Measure the size of the air duct opening(the size of the “hole” )

the second measurement) is the height(vertical measurement)

Actual outside measurement is 16" x 10"

If the hole is 20" wide by 14" tall

actual outside dimension is 16

10"x 4" (Duct Opening Size) 1-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 11.75" X 5.75" Measure the size of theFirst 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 10w X 4h is for duct opening measurement only, actual outsize overall dimensions is 11. 75 wide by 5. 75 high. If your duct opening size is 10 x 4, this is the right size and will fit in well. If you measure outside or surface size,