18" X 8" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 20 5/8" X 10 5/8"] Adjustable Return is fireproof and ensures efficient MFFG410-1 w6h6 actual front end outer

is fireproof and ensures efficient thermal performance

+ Product Details Size – 16"w X 22"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 24" OR 24" x 18" duct opening (measured at the opening)

actual front end outer dimensions are approximately 27 5/8" width X 27 5/8" height

18" X 8" Steel Return Air Filter Grille for 1" Filter Removable Frame [Outer Dimensions: 20 5 8" X 10 5 8"] Adjustable Return is fireproof and ensures efficient MFFG410 1 w6h6 actual front end outer is fireproof and ensures efficient thermal performance + Product Details Size – 16"w X 22"h is the size for the duct opening measurement only