The Luxair 125mm to 100mm ducting reducer collar
The Luxair 125mm to 100mm ducting reducer collar connects a 125mm (5") round ducting outlet to a 100mm (4") round ducting run — the transition fitting used when your cooker hood has a 125mm outlet spigot but your existing ducting run, wall duct sleeve, or external wall vent is sized for 100mm. The collar is push fit on both ends, and ducting tape is recommended around both joints to ensure a fully airtight seal — particularly important on a reducer fitting where any air leakage at the size transition will reduce extraction performance and allow cooking odours to escape into the void behind your cabinets.
When You Need a Reducer — And When You Don't
A reducer is needed in one specific situation — when the outlet size on your hood doesn't match the size of your ducting run. The most common scenario is a new cooker hood with a 125mm outlet being connected to an existing 100mm duct sleeve in the wall — common in older UK properties where 100mm ducting was installed as standard and a newer, higher-rated hood is being fitted. Rather than replacing the entire ducting run, a single reducer collar solves the mismatch at the connection point. However, it's important to understand the trade-off — reducing from 125mm to 100mm will restrict airflow compared to running 125mm throughout. For hoods rated above 450 m³/hr, Luxair recommends running the correct 125mm, 150mm, or larger ducting throughout rather than reducing, to maintain full extraction efficiency.
The Right Way to Use This Reducer
Fit the reducer at the hood outlet only — connecting the 125mm spigot on the hood to the start of a 100mm run. Do not use a reducer mid-run to reduce pipe size after a straight section of larger ducting, as this concentrates the airflow restriction at a single point and significantly increases motor noise. The reducer is a practical solution for connecting to an existing 100mm wall sleeve — it is not a substitute for correctly sized ducting throughout a new installation.
125mm to 100mm — Check Your Hood's Outlet Size First
Before ordering, confirm the outlet diameter on your specific hood. The outlet spigot is usually found on the top of the hood body and is clearly marked in the installation manual. Common UK outlet sizes are 100mm, 120mm, 125mm, 150mm, and 200mm — and they are not interchangeable. If your hood has a 120mm outlet rather than 125mm, this reducer will not fit — check Luxair's full reducer range for the correct size.
All the other components for your ducting run are available as related products at the bottom of this page — add everything to your basket in one visit.
Ducting Size Guide by Motor Rating
Using this reducer means your effective ducting size is 100mm throughout. Confirm your hood's motor rating is suitable for 100mm ducting before using this fitting:
- Below 450 m³/hr → 100mm ducting is correct
- 450–750 m³/hr → 125mm or 150mm ducting recommended
- 750–2000 m³/hr → 150mm or 200mm ducting recommended
If your hood is rated above 450 m³/hr, consider whether upgrading the wall sleeve to 125mm or larger is a better long-term solution than reducing.
