Some hoses included in the Vulcano® range have a TPU-coated steel spiral, to enhance the maximum adhesion to the wall and to ensure that the colour of the spiral remains unchanged over time and after exposure to atmospheric agents,  such as: Vulcano® M FR, Vulcano® R FR, Vulcano® 09 EST/ET, Vulcano® 15 EST/ET, Vulcano® Stone, Vulcano® Stone Plus, Vulcano® AF plus, Vulcano® 09 AF, Vulcano® 12 ET; in addition, the whole Next series features a TPU-coated steel spiral.