30"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 31.75"w x 25.75"h] Aluminum Bar + Product Details Size - 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size - 10"w X 18"h is the size for the duct opening measurement only

+ Product Details Size - 24"w X 28"h is the size for the duct opening measurement only

Actual Filter Size – 19 3/4"w x 24 3/4" x 1"

And The Cooler Air From Outside WIll Flow In From The Bottom

actual front end outer dimensions are approximately 21 5/8" width X 33 5/8" height

30"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 31.75"w x 25.75"h] Aluminum Bar + Product Details Size 4 X 12 Is CRFG2028 Width_14in + Product Details Size 10"w X 18"h is the size for the duct opening measurement only + Product Details Size 24"w X 28"h is the size for the duct opening measurement only