36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter with filter 1/2" White insulation will give

1/2" White insulation will give you a good R value of 3

+ Product Details Perfect Fit & Easy Sizing - Designed for a 22" x 36" OR 36" x 22" duct opening (measured at the opening)

Versatile Compatibility: Our ceiling grills aren't limited to just T bar drop ceilings

3-cone supply grille

With precise measurements and easy installation

36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter with filter 1/2" White insulation will give+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 34" OR 34" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 36. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 75" x 35. 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