16 in Backdraft Damper / Wall Shutter, 16 1/2 in x 16 1/2 in Opening Required/ GENERAL CHARACTERISTICS ITEM DESCRIPTION: ALUMINUM VANES,ENAMEL FINISH; RUST RESISTANT; SINGLE PANEL; FELTED FOR QUIET,WEATHERTIGHT CLOSURE; ATTACHED ROD ON FAN SIDE; 16 IN. FAN DIA; 19.125 IN. O/A SQ DIM.; 4.125 IN. BAKED ON STEEL SHROUD; 1.625 IN. FLANGE W/O.125 IN. MTG HOLES