The Master Flow 12" galvanized rotary turbine is an internally braced roof ventilator made of galvanized steel with an octagonal base. Its exclusive stainless dual bearing system offers durable, long-lasting, smooth and silent operation and double ribbed vanes, with convex top, direct wind-driven rain away from the unit. This turbine allows heat and moisture laden air to escape your attic, helping to extend the life of your roof. Its base is 18" in width and its overall height is 19 5/8". It can be installed on virtually any roof with a pitch from 2:12 to 12:12. It is protected by a limited lifetime warranty from the manufacturer.