Featuring permanently lubricated upper and lower ball bearings, the Lomanco 12-inch whirlybird turbine ventilator ensures long life and no maintenance. It reduces winter ice build-up, as well as energy bills. Made with all-aluminum, rust-free construction, this internally braced turbine ventilator withstands winds up to 147 MPH. With a rigid, spider-type structure, it"s riveted at every connection. The ventilator features 21 air-foil curved vanes with rolled vane edges to deflect water and a vari-pitch base that adjusts to a 12/12 roof pitch. Designed for residential use only, this turbine ventilator comes with a lifetime warranty.