12" standard externally braced wind turbine attic exhaust vent. Galvanized steel construction - mill finish. Co-polymer bearing system for quiet, long lasting, and smooth operation - adjusts to 6/12 pitch. Tested to ensure durability and performance in extreme temperatures and high winds. This exhaust vent requires adequate soffit intake vents. Requires 432 sq. in. of NFA (Net Free Area). Includes: Base and riser. Lifetime limited warranty.