For use with all types of flat roofs with bituminous or multi-layer waterproofing membranes. Use threaded outlets (female BSP thread) and threaded adaptor where additional length of spigot is required, i.e. where the joint to pipework is located within the concrete slab or in an inaccessible roof void | For "Warm roof" installations a foam insulation layer is factory applied as an option | Anti Vortex Fins may be fitted to dome grates to increase flow performance. Supplied with the roof outlet.