Why this ducting earns its place
Most extraction hoods have square ducting built in. Most ductwork runs are round. Someone has to join them up, and that someone is this converter.
It sits between your hood's 400 × 400 mm square flange and the start of your 300 mm round ducting. The inside geometry tapers smoothly from square to circle, which means air flows properly instead of hitting a wall and swirling back. The shape matters — a sloppy transition kills airflow and makes your extraction fan work twice as hard.
At 400 × 400 × 280 mm, it's chunky enough to do the job right, and light enough for one person to position. Duct-band it to the hood and duct-band it to your round ductwork, and you're ready to run.
