6" x 26" or 26" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 28.5"] 18" Round Duct Pipe Actual Filter Size – 33

Actual Filter Size – 33 3/4"w x 9 3/4" x 1"

actual front end outer dimensions are 15

+ Product Details Size – 16" x 36" or 36" x 16" is the size for the duct opening measurement only

very easy to do

+ Product Details Size - 28"w X 6"h is the size for the duct opening measurement only

6" x 26" or 26" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 28.5"] 18" Round Duct Pipe Actual Filter Size – 33+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 26" or 26" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 28. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 75" x 25. 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 Made