The Ubbink OFT-1A/166 is a 166mm diameter capped stack breather vent for use in asphalt roofs The OFT/1A has an integral collar and separate aluminium flange to withstand the high temperature during installation in asphalt roofs. The OFT/1A is suitable for use with soil & vent systems and for both mechanical and natural (passive) ventilation installations. Properties Height above roof: 300mm Flange diameter: 450mm Depth below flange: 350mm Free vent area: 20,000mm2 Pressure/airflow resistance: 1.0 Pa Material Type A: polyethylene stack / aluminium flange. Colour: black.