36"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - White [Outer Dimensions 37.75"w x 37.75"h] Ceiling By simply measuring the width

By simply measuring the width or the length of the vent

Actual Filter Size – 7 3/4"w x 27 3/4" x 1"

this guard fits almost any thermostat and blends seamlessly into any setting

+ Product Details Perfect Fit & Easy Sizing - Designed for a 20" x 18" OR 18" x 20" duct opening (measured at the opening)

36"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - White [Outer Dimensions 37.75"w x 37.75"h] Ceiling By simply measuring the width+ Product Details Size 36"w X 36"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 37. 75" Width X 37. 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