Roof Curb, For Fan Base Size 22 in, Curb Height 12 in, Curb Inside Width 17 1/2 in, Curb Outside Width 20 1/2 in, Material Steel, Standards UL 705, For Use With 22 in Square Base, Adjustability Fixed, Ventilation Type Nonventilated, Application General Exhaust, Curb Inside Length 17.5, Curb Outside Length 20 1/2 in, Curb Shape Square, Damper Tray Size 15 in x 15 in, Features Flashing Flange, One Welded Corner, Wood Nailer, Finish Galvanized, Flashing Flange Width 2 in