8" x 28" or 28" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 30.5"] w6h6 Its locking eight-tumbler mechanism and

Its locking eight-tumbler mechanism and supplied key safeguard your thermostat from tampering

+ Product Details Size - 12"w X 24"h is the size for the duct opening measurement only

+ Product Details Size – 24"w X 12"h is the size for the duct opening measurement only

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+ Product Details Size - 36"w X 36"h X 2"d (for duct opening measurement only)

8" x 28" or 28" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 30.5"] w6h6 Its locking eight-tumbler mechanism and+ Product Details Perfect Fit & Easy Sizing Designed for a 8" x 28" or 28" x 8" duct opening (measured at the opening), with actual outer dimensions of 10. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 7. 75" x 27. 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