16" x 30" or 30" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 12in diameter these heavy-duty louvers are ideal

these heavy-duty louvers are ideal for use in attics

actual front end outer dimensions are approximately 14 5/8" width X 20 5/8" height -

+ Product Details Size - 36"w X 6"h is the size for the duct opening measurement only

with actual outer dimensions of 8

+ Product Details Size – 6" x 18" or 18" x 6" is the size for the duct opening measurement only

16" x 30" or 30" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 12in diameter these heavy-duty louvers are ideal+ Product Details Perfect Fit & Easy Sizing Designed for a 16" x 30" OR 30" X 16" duct opening (measured at the opening), with actual outer dimensions of 18. 5" W x 32. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 15. 75" x 29. 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