8" X 4" [Duct Opening] 2-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"H X 5.75"H] w18h18 + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

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

Actual Filter Size – 15 3/4"w x 31 3/4" x 1"

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

actual front end outer dimensions are approximately 35

Actual Filter Size – 9 3/4"w x 9 3/4" x 1"

8" X 4" [Duct Opening] 2 Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"H X 5.75"H] w18h18 + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 26"w X 26"h is the size for the duct opening measurement only Actual Filter Size – 15 3 4"w x 31 3 4" x 1"