Master Flow 50 in. NFA Aluminum Square-Top Roof Vent in Weatherwood Perfect Utility Vent: Recommended for kitchen duct outlets and bathroom fan exhausts, as well as attic ventilation Large Capacity: Full 50 sq. in. of net free ventilating area (NFA) per vent Available with square throat in heavy duty aluminum Easier To Drilled-drilled nail holes with extra wide flashing area Finish: White