28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 8in Actual Filter Size – 33

Actual Filter Size – 33 3/4"w x 29 3/4" x 1"

+ Product Details Size - 10"w X 26"h is the size for the duct opening measurement only

+ Product Details Size - 18"w X 20"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 36 5/8" width X 14 5/8" height

28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 8in Actual Filter Size – 33+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 17. 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