36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return Actual Filter Size – 21

Actual Filter Size – 21 3/4"w x 11 3/4" x 1"

+ Product Details Size – 22"w X 18"h is the size for the duct opening measurement only

Ideal for Walls & Ceilings: Designed for seamless installation in standard 12" X 8" duct openings

+ Product Details Size - 18"w X 16"h is the size for the duct opening measurement only

36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return Actual Filter Size – 21+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 34" OR 34" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 36. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 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