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 + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 8" OR 8" x 28" duct opening (measured at the opening)

optimizing performance and energy efficiency

and the second number represents the height

actual front end outer dimensions are approximately 34 5/8" width X 34 5/8" height

Actual Filter Size – 27 3/4"w x 25 3/4" x 1"

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 + Product Details Perfect Fit+ 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