12"x 6" (Duct Opening Size) 1-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 13.75" X 7.75" it refers to the size

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

• Yellow PVC Coating to help resist corrosion and wear

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

2-Pack 5FT Red/Blue Lined Stainless Steel Braided Washing Machine Hoses with Universal 3/4" 90 degree connector

This great product also comes with 10-year warranty for quality related issues

12"x 6" (Duct Opening Size) 1-Way Stamped Face Steel Ceiling/sidewall Air Supply Register - Vent Cover - Actual Outside Dimension 13.75" X 7.75" it refers to the sizeFirst 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,