Roof Curb For Fan Base Size 26 in Curb Height 12 in Curb Inside Width 21 1/2 in Curb Outside Width 24 1/2 in Material Steel Standards UL 705 For Use With 26 in Square Base Adjustability Fixed Ventilation Type Nonventilated Application General Exhaust Curb Inside Length 21.5 Curb Outside Length 24 1/2 in Curb Shape Square Damper Tray Size 19 in x 19 in Features Flashing Flange One Welded Corner Wood Nailer Finish Galvanized Flashing Flange Width 2 in