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

+ Product Details Size - 20"w X 8"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 10" x 20" duct opening (measured at the opening)

Actual Filter Size – 11 3/4"w x 33 3/4" x 1"

+ Product Details Size – 30"w X 28"h is the size for the duct opening measurement only

which the interior PET provides

6"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Brown [Outer Dimensions 7.75"w x 7.75"h] Color_Anodized Aluminum + Product Details Size -+ Product Details Size 6"w X 6"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 7. 75" Width X 7. 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