Manthorpe Cross Flow Panel Vent - 450mm Rafter Centres (Box Of 50) The G455 Cross Flow Fly Screen Panel is designed for open eaves or cottage style situations and to provide a clear air passage between the roof felt and loft insulation. The fly screen section consists of evenly punched holes specifically designed to prohibit the entrance of large insects but wide enough not to be blocked by debris, paint or water droplets (see BS5250 section 6) The G455 is suitable for 450mm rafter centres 400mm and 600mm versions are also available. Colour Black  Material Lightweight Rigid PVC Manufacturing Process Vacuum Formed  Free Airflow 10,000mm/M equivalent to a continuous gap of 10mm