Backdraft Exhaust Damper, No Flange, Horizontal or Vertical Mount, Damper Size (In.) 17-3/4 x 17-3/4, Overall Size (In.) 17-3/4 x 17-3/4, Flange Width (In.) -, Max. Velocity (FPM) 2,000, Construction Material G-90 Galvanized Steel Frame and Aluminum Blades, Use w/Dayton Ventilators -, Includes Pre-punched Conduit Hole Knock-out and Felted Edges For Quiet Operation