20"w X 10"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 11.75"h] Ceiling actual front end outer dimensions 4 X 12 Is CRFG2028 Width_14in

actual front end outer dimensions are approximately 22 5/8" width X 52 5/8" height

+ Product Details Perfect Fit & Easy Sizing - Designed for a 6" x 10" or 10" x 6" duct opening (measured at the opening)

1/4" - 6518 PSI

Optional Butterfly Damper Available At Asin: B007CNEL1W

+ Product Details Size - 14"w X 34"h X 2"d (for duct opening measurement only)

20"w X 10"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 21.75"w x 11.75"h] Ceiling actual front end outer dimensions 4 X 12 Is CRFG2028 Width_14in actual front end outer dimensions are approximately 22 5 8" width X 52 5 8" height + Product Details Perfect Fit & Easy Sizing Designed for a 6" x 10" or 10" x 6" duct opening (measured at the opening)