This is a low profile cowl vent with a large cowl providing a ventilation area of 20 000mm2.The CV20K is available in 2 sizes: 600 x 300mm and 500 x 500mm designed for use with 500 x 250mm slates and features a simulated joint line. Please note due to production times any orders over 4 vent tiles will be on an estimated lead time of 7 to 10 working days. Cowl incorporates barriers to prevent water ingress and block wind driven rain, allowing the water to drain away down slope. Factory fitted round felt sleeve, significantly reducing the felt tearing that can occur around rectangular spigots. Ventilation Area: 20 000mm2 Airflow Resistance: 9.5 Pascals at 30 litres per sec Water Resistance: Exceeds all relevant parts of DoE Partners in Technology Programme Roof Pitches: Over 20