WTI12BX 12" Internally Braced Galvanized Turbine With Base, Brown, Ventilates Based On Wind, 345 CFM At 5 MPH Winds, 544 CFM At 8 MPH Winds & 969 CFM At 15 MPH Winds, Patented Dupont Delrin Bearings, Works On Roof Pitches 3/12 to 12/12, 2 Year Limited Warranty.