18" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 20 5/8" X 20 5/8"] Ceiling + Product Details Size - Compatible with Duct 4" RG1612AL actual front end outer

+ Product Details Size - 36"w X 22"h is the size for the duct opening measurement only

+ Product Description Enhance your ventilation system with our high-quality grilles and registers

Actual Filter Size – 23 3/4"w x 13 3/4" x 1"

+ Product Details Size – 12"w X 20"h is the size for the duct opening measurement only

Upgrade today for better performance and cleaner air

18" X 18" Steel Return Air Filter Grille for 1" Filter Removable Frame [Outer Dimensions: 20 5 8" X 20 5 8"] Ceiling + Product Details Size Compatible with Duct 4" RG1612AL actual front end outer + Product Details Size 36"w X 22"h is the size for the duct opening measurement only + Product Description Enhance your ventilation system with our high quality grilles and registers