It is a high-temperature flexible duct for moving air where an ordinary hose would fail - hot air feeds and returns, brake and diff cooling ducts, engine bay ventilation, motorsport cockpit cooling, marine engine room ventilation and industrial hot air handling. The two layers of silicone-coated glass fibre with a steel wire helix give it heat resistance far beyond a plastic or rubber duct.

The operating range is -70C to +310C, which is the reason most people choose it over cheaper ducting. That covers hot air off a radiator or intercooler, brake cooling ducts running close to hot discs, and industrial process air. For comparison, PVC ducting tops out around +65C - if your application is anywhere near hot components, this is the material you need.

Internal diameters from 25mm up to 200mm, in 1, 2, 3 and 4 metre lengths. Order by internal diameter to match the spigot or duct outlet it will slide over. Because the wall is flexible, the duct will stretch slightly onto a spigot that is a close fit, which makes for a neat joint.

The wire helix moulded into the wall stops the duct collapsing under suction and stops it crushing flat if something rests against it. That means it works on both the pressure and the suction side of a fan or blower, and it will hold its bore in a tight installation. Without a helix, any flexible duct will pull shut the moment you apply negative pressure.

Yes, for anything demanding. The double layer gives more mechanical strength, better insulation of the air inside the duct, and a longer service life under vibration and heat cycling. Single-ply duct is fine for gentle ventilation work; if the duct will be handled, routed tightly, or run continuously at high temperature, the double layer is the better buy.

Black, red, blue and grey. Black and grey are the usual choice for industrial and marine installations where the duct should not draw attention; red and blue are popular on motorsport and show builds where the ducting is visible. The colour is cosmetic only - the specification is identical across all four.