20" x 4" Aluminum Spiral Duct Air Vent Grille Cover - Fully Adjustable Double Deflection HVAC Air Supply [Outer Dimensions: 22w X 6"h] Insulated Line + Product Details Size -

+ Product Details Size - 26"w X 18"h is the size for the duct opening measurement only

[Outer Dimensions: 20

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

Marked circles for cutout

20" x 4" Aluminum Spiral Duct Air Vent Grille Cover - Fully Adjustable Double Deflection HVAC Air Supply [Outer Dimensions: 22w X 6"h] Insulated Line + Product Details Size -+ Product Details Size 20"w X 4"h is the size for the duct opening measurement only, actual front end outer dimensions are 22" width X 6" height. Design 180 degrees double direction adjustable fins are manually adjustable individually for optimal air distribution. High Quality Commercial grade aluminum will never rust designed for warehouses, factories, workshops, gymnasiums & restaurants Airflow Easy unrestricted airflow for your HVAC system.