10" X 18" or 18" X 10" Heavy Duty Floor Grille - Fixed Blades Air Grille - Brown [Outer Dimensions: 11.75 X 19.75] Insulated Line + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 16"w X 18"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening)

+ Product Details Size – 18"w X 12"h pleated MERV 2 filter for HVAC return filter grille - 12 Pack

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 10" OR 10" X 18" duct opening (measured at the opening)

Actual Filter Size – 7 3/4"w x 23 3/4" x 1"

10" X 18" or 18" X 10" Heavy Duty Floor Grille Fixed Blades Air Grille Brown [Outer Dimensions: 11.75 X 19.75] Insulated Line + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 16"w X 18"h is the size for the duct opening measurement only + Product Details Perfect Fit & Easy Sizing Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening)