12" x 10" or 10" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 12.5"] Ceiling + Product Details Size -

+ Product Details Size - 36"w X 26"h is the size for the duct opening measurement only

Rigid gauge built for durability and long life in mind

Complies with industry standards of USA: ASTM D-882

actual front end outer dimensions are approximately 22 5/8" width X 42 5/8" height -

+ Product Description Protect your thermostat with the durable and tamper-proof Beige Metal Thermostat Guard

12" x 10" or 10" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 12.5"] Ceiling + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 10" or 10" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 12. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 75" x 9. 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