6"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 13.75"h] return filter + Product Details Size –

+ Product Details Size – 6" x 18" or 18" x 6" is the size for the duct opening measurement only

Actual Filter Size – 33 3/4"w x 15 3/4" x 1"

+ Product Details Perfect Fit & Easy Sizing - Designed for a 36" x 26" OR 26" x 36" duct opening (measured at the opening)

+ Product Description Enhance your HVAC system with our premium Aluminum Double Deflection Adjustable Air Supply Diffuser

6"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 13.75"h] return filter + Product Details Size –+ Product Details Size 6"w X 12"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 7. 75" Width X 13. 75" Height Weather and Pest Proof These louvers are especially designed to prevent water from entering your home, and with a built in back 1 2" mesh they also protect you from annoying rodents like mice, rats, birds, and squirrels High Quality Aluminum The premium durable aluminum will never rust and it will never wear