34" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Round Duct Pipe + Product Details Size –

+ Product Details Size – 18" x 34" or 34" x 18" is the size for the duct opening measurement only

Tamper-Proof Design – Provides robust protection to prevent unauthorized access and ensure consistent thermostat settings

+ Product Details Size – 22"w X 20"h is the size for the duct opening measurement only

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Filter Size - 33

34" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Round Duct Pipe + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 34" x 12" Or 12" x 34" duct opening (measured at the opening), with actual outer dimensions of 36. 5" W x 14. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 33. 75" x 11. 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