16" X 16" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 17.75"W X 17.75"H] Aluminum - Cube Core Actual Filter Size – 21

Actual Filter Size – 21 3/4"w x 17 3/4" x 1"

+ Product Details Size - 28"w X 16"h is the size for the duct opening measurement only

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

+ Product Details Size – 12"w X 18"h is the size for the duct opening measurement only

Actual Filter Size – 24 3/4"w x 25 3/4" x 1"

16" X 16" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 17.75"W X 17.75"H] Aluminum - Cube Core Actual Filter Size – 21+ Product Details Size 16"w X 16"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 17. 75" width X 17. 75" height. High Quality High quality steel with counter sunk screw holes (screws included) and no sharp edges. Equipped with a lever for easy airflow adjustment and dampening. Airflow Control Adjustable airflow lever allows precise control over the direction and volume of air. Installation