8" x 8" [Duct Opening] Ceiling Supply Diffuser Vent Cover – 4-Way Airflow with Full Aluminum Frame, Back Blades & Opposing Blade Lever Damper [Outer Size: 11" x 11"] Aluminum Adjustable Curved Blade 25" X 20"opening dimension (vent

25" X 20"opening dimension (vent opening) - actual total grille size is approx

+ Product Details Size - 20"w X 28"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 26" x 18" OR 18" x 26" duct opening (measured at the opening)

Its precise dimensions ensure a perfect fit for your air duct openings

Design – Circular air supply valves - designed to be used in low and medium pressure ventilation air conditioning systems

8" x 8" [Duct Opening] Ceiling Supply Diffuser Vent Cover – 4-Way Airflow with Full Aluminum Frame, Back Blades & Opposing Blade Lever Damper [Outer Size: 11" x 11"] Aluminum Adjustable Curved Blade 25" X 20"opening dimension (vent+ Product Details Size Refers to duct opening only. The face frame extends roughly 1. 5" on each side. Do not measure the overall grille for sizing. Design All aluminum frame and back blades. Rustproof and built to last in moisture prone environments. Quiet Airflow Opposing blade damper design reduces vibration and noise for smoother air distribution. Clean Finish White powder coated surface resists chips, scratches, and discoloration over time. Easy