36"w X 16"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 17.75"h] Return + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 10" x 18" or 18" x 10" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 30 5/8" width X 34 5/8" height

"Opposing" back blades

+ Product Details Size - 25"w X 32"h is the size for the duct opening measurement only

Designed for sidewall and ceiling installation with included screws

36"w X 16"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 37.75"w x 17.75"h] Return + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 10" x 18" or 18" x 10" is the size for the duct opening measurement only actual front end outer dimensions are approximately 30 5 8" width X 34 5 8" height