Efficient way of extracting or taking off air from duct work. Manufactured from galvanised or plated sheetmetal. BM & BMD come complete with seal. BM & BMD have pre-drilled holes in the face to allow for easier fixing to ductwork. All spigots come complete with flexible duct holding tabs. All spigots have an extended quadrant to give greater room for duct taping to spigot.