Exhaust Fan Venturi Frame For Blade Diameter 16 in Includes Mounting Bolts Slotted Motor Base Overall Depth 8 1/2 in Overall Height 20 in Overall Width 20 in Venturi Depth 3 in Flange Width 1 in For Cut-Out Height 18 1/2 in For Cut-Out Width 18 1/2 in Frame Finish Galvanized Material Steel Opening Diameter 18 1/2 in