Flange-shut-off-flaps-and-grid-set for 240mm RoofWhirly4Africa roof mounted wind turbine ventilator (aka whirlybird vent) Posted on July 20, 2016August 28, 2020 by whirlyadmin Grid and flange set for 240mm RoofWhirly4Africa roof mounted wind turbine ventilator (aka whirlybird vent)