Flexible aluminium ducting that holds its shape once positioned - you bend it to the route you need and it stays there, rather than needing supporting along its length. It is used in heating, ventilation and air conditioning work, and for moderate-temperature extraction.

76mm, 102mm, 125mm and 150mm internal diameter, in 2 and 4 metre lengths. Order by internal diameter to match the spigot or outlet it slides over. Those four sizes cover the great majority of domestic and light commercial HVAC and extraction work.

-30C to +150C, and it is manufactured to EN 13501-1, the European fire classification standard for building materials. That temperature range is well beyond PVC or polyurethane ducting, which is the main reason to choose it over a cheaper plastic duct.

HVAC runs, cooker hood and bathroom extraction, warm air distribution, and vehicle and workshop ventilation where the air is warm but not hot. For genuinely hot air - engine exhaust, process air above 150C - you need silicone glass fibre ducting at -70C to +310C instead.

Snips or tin snips, cutting carefully round the profile. Wear gloves - cut aluminium ducting leaves sharp edges that will find your hands. Dress the cut end before fitting so it cannot cut into a seal or catch on anything during installation.

Slide it over the spigot and secure with a worm drive clip or a ducting clamp, and seal the joint with duct tape if the system needs to be airtight. Because it is semi-rigid it holds position at the joint while you fit the clamp, which makes installation considerably easier than with a floppy duct.