20"w X 20"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: 21.125" X 21.125"] Black + Product Details Size –

+ Product Details Size – 16" x 34" or 34" x 16" is the size for the duct opening measurement only

Actual Filter Size – 27 3/4"w x 15 3/4" x 1"

+ Product Details Size – 18"w X 14"h is the size for the duct opening measurement only

Design – rigid gauge built for durability and long life in mind

Actual Filter Size – 24 3/4"w x 23 3/4" x 1"

20"w X 20"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: 21.125" X 21.125"] Black + Product Details Size –+ Product Details Size 20"w X 20"h Is The Size For The Duct Opening Only, Dimensions With Outer End are 21. 125" X 21. 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