Galvanized Tapered Reducer
The cone-shaped fitting that steps a round duct down to a smaller diameter, smoothly.
AirGreen codeAG-VC-00307
514 316-2973 · sales@airgreen.ca
Quick facts
The galvanized tapered reducer connects two round ducts of different diameters. Its cone-shaped body takes the air from the large diameter to the small one gradually, with no abrupt narrowing. It is available in eleven combinations, from 4 × 3 in to 12 × 10 in.
Keeping the right air velocity to the end of the system
In a forced-air system, the main duct loses part of its airflow at each branch. Reducing it by one size after a group of take-offs helps keep a steady air velocity all the way to the last outlet. The reducer is also used to bring a branch down to the collar diameter of a floor register, a fan or an air exchanger.
How to read the size
The first figure is the large diameter, the second the small one: a 10 × 8 in connects a 10 in duct to an 8 in duct. Measure both sides on site before ordering, especially on an existing duct.
- One-size reductions: 4 × 3, 5 × 4, 6 × 5, 7 × 6, 8 × 7, 10 × 8, 12 × 10 in
- Reductions of two sizes or more: 6 × 4, 7 × 5, 8 × 5, 8 × 6 in
Installation
Fit the pieces together, secure each joint with sheet metal screws and seal with aluminum tape or mastic. Do not go below the diameter set in the system design calculation: the room served would be short of air.
Supplied and installed by AirGreen across Greater Montréal
Our crews design and install duct systems 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 both diameters and the quantity.
Stepping the duct down branch by branch
Once part of the air has left through a branch, the duct that continues can be smaller: the tapered reducer makes that change.
- Reducing a round trunk after a take-off or a wye
- Bringing a branch down to the collar size of a boot
- Connecting a duct to the smaller collar of a fan or appliance
- Matching a new run to an existing duct of another diameter
11 sizes, one page
Each size has its own AirGreen code. Tap a row to select it.
| Dimensions | AirGreen code |
|---|---|
| 4 × 3 in | AG-VC-00301 |
| 5 × 4 in | AG-VC-00302 |
| 6 × 4 in | AG-VC-00303 |
| 6 × 5 in | AG-VC-00304 |
| 7 × 5 in | AG-VC-00305 |
| 7 × 6 in | AG-VC-00306 |
| 8 × 5 in | AG-VC-00307 |
| 8 × 6 in | AG-VC-00308 |
| 8 × 7 in | AG-VC-00309 |
| 10 × 8 in | AG-VC-00310 |
| 12 × 10 in | AG-VC-00311 |
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 × small: an 8 × 6 in joins an 8 in duct to a 6 in duct.
- Check both actual diameters on site: unit collar, existing duct, boot.
- Fasten both joints with sheet-metal screws and seal them with foil tape or mastic.
- Do not reduce a branch below the size the duct design calls for: the room it serves would be short of air.
You may also need
Galvanized Straight Reducer
Galvanized Round Pipe – 60 in Length
Galvanized Side Take-Off
Galvanized Wye Fitting
Adjustable Galvanized Round 90° Elbow
Galvanized Round End Cap
Cleats for Galvanized Duct (C and S)
Galvanized Oval Duct – 60 in LengthVentilation ductsSee all
Frequently asked questions
How do I read 7 × 5 in?
The reducer takes a 7 in duct on one side and a 5 in duct on the other.
Tapered or straight reducer?
Both step a round duct down to a smaller diameter. The tapered one does it through a cone-shaped body; pick the shape that suits the space and the sizes you need, or ask us.
Can a trunk be reduced?
Yes, it is common: after each group of branches, the trunk can drop one size, as the duct design calls for.
Can you install it?
Yes. We design and install forced-air and ventilation duct systems across Greater Montréal.
Diameter transitions done right
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.