12" x 36" or 36" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Grille Efficient Airflow Design: The slots

Efficient Airflow Design: The slots are meticulously angled to diversify airflow in two directions

+ Product Details Size - 4"w X 16"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 36 5/8" width X 32 5/8" height

75"H – fits a 16" X 12" duct opening

12" x 36" or 36" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Grille Efficient Airflow Design: The slots+ 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