8" x 20" or 20" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 22.5"] 10" Round Duct Pipe these heavy-duty louvers are ideal

these heavy-duty louvers are ideal for use in attics

actual front end outer dimensions are approximately 38 5/8" width X 18 5/8" height -

+ Product Details Size – 12" x 18" or 18" x 12" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 28 5/8" width X 32 5/8" height

this guard ensures long-lasting protection and security

8" x 20" or 20" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 22.5"] 10" Round Duct Pipe these heavy-duty louvers are ideal+ Product Details Perfect Fit & Easy Sizing Designed for a 8" x 20" or 20" x 8" duct opening (measured at the opening), with actual outer dimensions of 10. 5" W x 22. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 7. 75" x 19. 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