16" x 18" or 18" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Insulated Line Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 18" X 10" duct openings

+ Product Details Size – 18"w X 25"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 10" or 10" x 8" duct opening (measured at the opening)

+ Product Details Size - 22"w X 4"h is the size for the duct opening measurement only

Say goodbye to pest-related worries as the built-in back 1/2" mesh acts as a barrier against unwanted rodents like mice

16" x 18" or 18" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Insulated Line Ideal for Walls & Ceilings:+ Product Details Perfect Fit & Easy Sizing Designed for a 16" x 18" OR 18" X 16" duct opening (measured at the opening), with actual outer dimensions of 18. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 15. 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