18" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Supply Grille + Product Details Size -

+ Product Details Size - 20"w X 12"h is the size for the duct opening measurement only

12"w X 6"h Is The Size For The Duct Opening Measurement Only

actual front end outer dimensions are 19

from 4" to 20"

75" width X 33

18" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Supply Grille + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 34" OR 34" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 36. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 33. 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