18" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w25h25 + Product Details Size –

+ Product Details Size – 20"w X 20"h is the size for the duct opening measurement only

+ Product Details Size - 8"w X 20"h is the size for the duct opening measurement only

Exceptional Craftsmanship: Hand-inspected for quality

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 24" or 24" x 12" duct opening (measured at the opening)

Actual Filter Size – 23 3/4"w x 17 3/4" x 1"

18" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w25h25 + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 20. 75" x 20. 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 Made from