18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 12in diameter And The Cooler Air From

And The Cooler Air From Outside WIll Flow In From The Bottom

actual front end outer dimensions are approximately 12 5/8" width X 8 5/8" height

+ Product Details Size - 22"w X 24"h 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 – 12" x 34" or 34" x 12" is the size for the duct opening measurement only

18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 12in diameter And The Cooler Air From+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 36" OR 36" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 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