Hambleside Danelaw Universal Slate Roof Vent - Airflow 5000mm2 (Black) Not suitable for mechanical extraction - Cannot connect soil pipe   Universal slate roof ventilator for man made or natural slates. Sizes to suit either 600 x 300mm or 500 x 250mm slates. Minimum rafter pitch: 22.5 degrees or 25 degrees depending on head lap.   Actual ventilation area 5,000mm2 Available in Black as standard, Grey to order. Recycled content up to 50% (Black polypropylene)