From 710mm

Every spiral duct reducer here has a 710mm (approx. 28″) large end, stepping down to 7 smaller diameters, from 630mm right down to 355mm. Use one wherever your ductwork steps down in diameter — after a branch take-off, at a fan spigot or where space tightens. Alpha Air is a Leicester-based ventilation supplier — these reducers are made to order and despatched in 3-5 working days.

For reducers starting from other diameters, see all spiral duct reducers.