Roof Curb For Fan Base Size 25 in to 30 1/2 in Curb Height 12 in Curb Inside Width 19 1/2 in to 28 in Curb Outside Width 23 1/2 in to 32 in Material Steel Standards UL 705 For Use With 25 in to 30 1/2 in Square Base Adjustability Adjustable Ventilation Type Nonventilated Application General Exhaust Curb Shape Square Damper Tray Size 19 in to 27 in Features Flashing Flange Finish Galvanized Flashing Flange Width 4 in For Fan Type Downblast Fans Filtered Supply Fans Upblast Fans