The spiral spring steel wire comes with a wall of pure polyester polyurethane with flame-retardant additives.
It is in accordance to DIN ISO 4649. It is more abrasion-resistant than poly-ether polyurethane. The wall thickness between spirals is approximately 0.5mm.
It is protective against mechanical wear and is rarely flammable. It is used as a transport hose for abrasive solids, in wood processing machines and in shavings extractions in wood processing.