Efficient and durable primary roof ventilator supplied in convenient 1m lengths. OF1 provides ventilation equivalent to a continuous 10mm opening (10,000mm²) and is used to ventilate pitched roofs of 15°> and the roof voidEfficient and durable primary roof ventilator supplied in convenient 1m lengths. OF1 provides ventilation equivalent to a continuous 10mm opening (10,000mm²) and is used to ventilate pitched roofs of 15°> and the roof void is uninhabited loft or attic space....View more