Glidevale In-line ridge ventilators have been designed to provide an aesthetic and unobtrusive solution to roof ventilation at ridge level. Guaranteed actual nett free ventilation area: 12,000mm2. 2.4m spacing to achieve 5000mm2 per metre.AA fire rated angle ridge vent.Can be converted to a soil pipe or mechanical extraction terminal with an SUA adapter. Maximum pitch when used with dry ridge systems: G51 - 45°, G53 - 40°, G54 - 40°, G64 - 45°.