18" x 30" or 30" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w18h18 + Product Details Size –

+ Product Details Size – 14" x 36" or 36" x 14" is the size for the duct opening measurement only

We carry sizes the big box stores don't

actual front end outer dimensions are 16" width X 8" height

Actual Filter Size – 15 3/4"w x 25 3/4" x 1"

18" x 30" or 30" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w18h18 + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 30" OR 30" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 32. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 29. 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