Galvanized Straight Reducer
The reducer that adapts a round duct to an appliance collar or an existing duct of another diameter.
AirGreen codeAG-VC-00405
514 316-2973 · sales@airgreen.ca
Quick facts
The galvanized straight reducer connects one round duct to another of smaller diameter while keeping both on the same axis. It is mainly used to connect a duct to a unit’s collar — fan, air exchanger, range hood — or to an existing duct that does not match the diameter of the new section.
When the duct and the collar are not the same diameter
On a renovation job, it is common for a fan to have a 5 in collar while the existing system is 6 in, or for a new section to have to meet an old duct of another size. Instead of crushing or cutting the sheet metal, the reducer makes a clean transition that can be screwed and sealed.
Seven sizes
The reducer is available in 5 × 4, 6 × 4, 6 × 5, 7 × 6, 8 × 6, 10 × 8 and 12 × 10 in. The first number is the large diameter, the second the small one. For another combination, see also our tapered reducer, available in eleven sizes.
Before reducing a unit’s duct
- Measure the unit’s actual collar, not just the size printed on the box.
- Check the minimum diameter required by the unit’s manufacturer: a duct that is too small reduces airflow and increases noise.
- Screw and seal both joints with aluminum tape or mastic.
Installed by AirGreen in Greater Montréal
We connect fans, air exchangers and forced-air units to their ducts in Montréal, Laval, Longueuil, on the South Shore and on the North Shore. RBQ licence 5645-9605-01, subcategory 15.8 Ventilation. For availability or a quote, call us at 514 316-2973 or email sales@airgreen.ca with the two diameters to connect and the quantity.
The link between two diameters that don’t match
The collar on a fan, an air exchanger or a hood is not always the size of the planned duct: the straight reducer bridges the gap.
- A 6 in duct connected to a fan’s 5 in collar
- Connecting an air exchanger or an in-line fan to a smaller duct
- Partial replacement where the old and new ducts differ
- Reducing a branch ahead of a floor boot
7 sizes, one page
Each size has its own AirGreen code. Tap a row to select it.
| Dimensions | AirGreen code |
|---|---|
| 5 × 4 in | AG-VC-00401 |
| 6 × 4 in | AG-VC-00402 |
| 6 × 5 in | AG-VC-00403 |
| 7 × 6 in | AG-VC-00404 |
| 8 × 6 in | AG-VC-00405 |
| 10 × 8 in | AG-VC-00406 |
| 12 × 10 in | AG-VC-00407 |
Large diameter × small diameter, in inches.
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- Sizes read large diameter × small diameter.
- Measure the appliance collar: its actual diameter sets the small side of the reducer.
- Downsizing an appliance duct can cut its airflow: check the minimum duct size the appliance maker calls for.
- Screw and seal both joints with foil tape or mastic.
You may also need
Galvanized Tapered Reducer
Galvanized Round Pipe – 60 in Length
Fantech FG Series Inline Fan
Adjustable Galvanized Round 90° Elbow
Galvanized Round End Cap
Cleats for Galvanized Duct (C and S)
Galvanized Oval Duct – 60 in Length
90° Oval-to-Round Elbow (Oval Duct)Ventilation ductsSee all
Frequently asked questions
Can I connect a duct smaller than a fan’s collar?
Physically yes, but the fan loses airflow. Follow the duct size the appliance maker recommends.
How is it different from the tapered reducer?
Both join two round duct diameters. The size range differs; pick the part that offers your combination and fits the space, or ask us.
How do I know which size to order?
Measure the two diameters to join. The larger one is the first number, the smaller one the second.
Can you install it?
Yes. We connect fans, air exchangers and forced-air equipment to their ducts across Greater Montréal.
Clean, sealed appliance connections
Tell us the size and the quantity: we confirm availability and send you a quote. Or let our technicians install it for you.
Specifications from the manufacturer’s documentation, checked on October 7, 2026.