12"w X 12"h Extruded Aluminum Adjustable Core Mount Supply Ceiling HVAC Air Grille – Interchangeable: 1-Way, 2-Way, 3-Way or 4-Way - Vent Duct Cover [Outer Dimensions: 13.125" X 13.125"] ceiling and the second number represents

and the second number represents the height

actual front end outer dimensions are approximately 10 5/8" width X 28 5/8" height

10" x 4" Floor Register HVAC Air Supply Grille - Heavy Duty Rigid Built - Plastic Never Rust Vent Duct Cover

+ Product Details Size - 30"w X 10"h X 2"d (for duct opening measurement only)

12"w X 12"h Extruded Aluminum Adjustable Core Mount Supply Ceiling HVAC Air Grille – Interchangeable: 1-Way, 2-Way, 3-Way or 4-Way - Vent Duct Cover [Outer Dimensions: 13.125" X 13.125"] ceiling and the second number represents+ Product Details Size 12"w X 12"h Is The Size For The Duct Opening Only, Dimensions With Outer End are 13. 125" X 13. 125". Design Re configurable Interchangeable Sections Easily convertible into 1 Way, 2 Way, 3 Way, or 4 Way Just lift sections and rotate to re configure direction. High Quality Aluminum The premium durable aluminum will never rust and it will never wear through leaving the material with an elegant, beautiful, and smooth surface, adds