Brass sealed nozzle heaters are completely against external agents such as melted plastics. They are very resistant to wearing and shocks. High watt-density per square centimeter allows a fast and safe reaching of required working temperature. Brass sealed nozzle heaters are submitted to extremely high pressure that ensure high insulation, excellent thermal exchange, lack of internal voids, perfectly smooth contact area for an optimum and uniform heat transfer to every part of the nozzle.