32" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel diagonally feed it through the

diagonally feed it through the square hole

+ Product Details Perfect Fit & Easy Sizing - Designed for a 16" x 36" OR 36" X 16" duct opening (measured at the opening)

+ Product Details Size – 28"w X 18"h is the size for the duct opening measurement only

75"H – fits a 14" X 14" duct opening

32" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel diagonally feed it through the+ Product Details Perfect Fit & Easy Sizing Designed for a 32" x 18" OR 18" x 32" duct opening (measured at the opening), with actual outer dimensions of 34. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 31. 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