28"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 29.75"w x 31.75"h] Grilles + Product Details Size - Ducting Components RG2016 FBA-HP Applications The C box

+ Product Details Size - 24"w X 18"h is the size for the duct opening measurement only

each diffuser is carefully shrink-wrapped with a sturdy cardboard backing

+ Product Details Perfect Fit & Easy Sizing - Designed for a 26" x 12" OR 12" x 26" duct opening (measured at the opening)

+ Product Details Size – 28"w X 10"h is the size for the duct opening measurement only

+ Product Details Size - 25"w X 14"h is the size for the duct opening measurement only

28"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 29.75"w x 31.75"h] Grilles + Product Details Size Ducting Components RG2016 FBA HP Applications The C box + Product Details Size 24"w X 18"h is the size for the duct opening measurement only each diffuser is carefully shrink wrapped with a sturdy cardboard backing