12" x 36" or 36" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Outdoor Vent Covers + Product Details Outer dimensions:

+ Product Details Outer dimensions: 13

+ Product Details Size - 26"w X 30"h is the size for the duct opening measurement only

+ Product Details Size - 8"w X 30"h is the size for the duct opening measurement only

Actual Filter Size – 23 3/4"w x 33 3/4" x 1"

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12" x 36" or 36" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Outdoor Vent Covers + Product Details Outer dimensions:+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 36" or 36" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 75" x 35. 75" x 1" Premium Airflow Efficiency High performance cube core eggcrate design allows 95% airflow efficiency, reducing energy costs and maximizing HVAC system lifespan. Durable, Rust Free Aluminum