6" x 28" or 28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 30.5"] Material_Aluminum 5/8" - 2579 PSI

5/8" - 2579 PSI

Looks like it was just waxed

+ Product Details Size – 10" X 4" is the size for the duct opening (floor/vent hole) measurement only

Incorporated with Integral Butterfly Damper for full Airflow Control

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

6" x 28" or 28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 30.5"] Material_Aluminum 5/8" - 2579 PSI+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 30" or 30" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 32. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 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 Made