8" X 4" Adjustable AIR Supply Diffuser - HVAC Vent Cover Sidewall or Ceiling - Grille Register - High Airflow - Black w12h12 + Product Details Size –

+ Product Details Size – 28" x 30 or 30" x 28" is the size for the duct opening measurement only

Use appropriate fittings and avoid using excessive force when tightening connections

+ Product Details Size - 8"w X 8"h is the size for the duct opening measurement only

+ Product Details Size - The listed 10" diameter refers specifically to the size of the duct opening

+ Product Details Size - 20"w X 36"h is the size for the duct opening measurement only

8" X 4" Adjustable AIR Supply Diffuser - HVAC Vent Cover Sidewall or Ceiling - Grille Register - High Airflow - Black w12h12 + Product Details Size –+ Product Details Size 8"w X 4"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 9. 875" width X 6" height. High Quality High quality steel construction, no scuff powder coat durable finish, smooth, shiny, scratch resistant, no sharp edges, 2 recessed screw holes on each side with screws included, screws same color as vent cover, easy installation. Adjustable airflow control Adjustable airflow