28" X 28" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 30 5/8" X 30 5/8"] Powder-Coat Installs Directly On Round & Product Details Size 14 Material_Anodized Aluminum LR164

Installs Directly On Round & Oval Spiral Duct - No Frames

actual front end outer dimensions are approximately 30 5/8" width X 20 5/8" height

+ Product Details Size - 30"w X 18"h is the size for the duct opening measurement only

They seamlessly integrate into sheet rock plaster frame ceilings as well

+ Product Details Size – 20"w X 26"h is the size for the duct opening measurement only

28" X 28" Steel Return Air Filter Grille for 1" Filter Removable Frame [Outer Dimensions: 30 5 8" X 30 5 8"] Powder Coat Installs Directly On Round & Product Details Size 14 Material_Anodized Aluminum LR164 Installs Directly On Round & Oval Spiral Duct No Frames actual front end outer dimensions are approximately 30 5 8" width X 20 5 8" height