26"w X 22"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 27.75"w x 23.75"h] return filter and the second number represents Compatible With Duct 7in Applications This sheet metal DDAG-A-1212

and the second number represents the height

+ Product Details Size - 14"w X 12"h is the size for the duct opening measurement only

+ Product Details Size – 20"w X 30"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 12 5/8" width X 14 5/8" height

+ Product Details Size – 18" x 24" or 24" x 18" is the size for the duct opening measurement only

26"w X 22"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 27.75"w x 23.75"h] return filter and the second number represents Compatible With Duct 7in Applications This sheet metal DDAG A 1212 and the second number represents the height + Product Details Size 14"w X 12"h is the size for the duct opening measurement only