Features and benefits: • Efficient, unobtrusive and easy to fit • 4mm wide slots comply with BS 5250 : 2011 • Durable and totally resistant to decay • UV stabilised and colourfast Efficient strip type eaves ventilators (primary vent) for use on roofs where the eaves incorporate a soffit board of between 6 and 9mm in thickness. 1137 provides ventilation equivalent to a continuous 10mm opening (10,000mm² per metre run).