The Hambleside Danelaw universal refurbishment tray vent is installed into the eaves of a completed and traditionally constructed roof to ensure insulation does not block the path of air necessary to ventilate the roof space.To be used either as a single panel to rafter centres of 450mm or below 450mm by trimming the panel to suit. For rafter centres between 450mm and 600mm the panel can be extended by cutting a second panel in half and connecting the two. Properties Airflow: 25,000mm2 airflow per vent.Width: 397mm.Rafter spacings: universal.Material: PVC.Colour: black.