Specifications
- Inlet Width: 1" to 36"
- Inlet Height: 1" to 36"
- Outlet Width: 1" to 36"
- Outlet Height: 1" to 36"
- Length: 1" to 36"
- Materials: Galvanized Steel, Aluminum, Stainless Steel
- Gauges: 26, 24, 22, 20
- Connections: Raw, Slip, Drive, FoldOut, DoubleFoldOut
Standard Duct Transition Sizes & Pricing
| Input W×H | Output W×H | Length | Input Joint | Output Joint | Price | Order |
|---|---|---|---|---|---|---|
| 8"×6" | 6"×6" | 6" | Raw | Raw | $10.20 | |
| 8"×8" | 6"×6" | 6" | Raw | Raw | $11.40 | |
| 10"×8" | 8"×6" | 8" | Slip | Slip | $14.80 | |
| 10"×8" | 8"×8" | 8" | Slip | Slip | $15.60 | |
| 10"×10" | 8"×8" | 8" | Slip | Slip | $16.40 | |
| 12"×8" | 10"×8" | 8" | Slip | Slip | $16.80 | |
| 12"×10" | 10"×8" | 10" | Slip | Slip | $19.50 | |
| 12"×12" | 10"×10" | 10" | Drive | Slip | $22.30 | |
| 14"×10" | 12"×8" | 10" | Slip | Slip | $21.40 | |
| 14"×12" | 10"×10" | 12" | Drive | Slip | $26.80 | |
| 16"×10" | 12"×10" | 10" | Drive | Slip | $25.60 | |
| 16"×12" | 14"×10" | 12" | Drive | Drive | $32.40 | |
| 18"×12" | 14"×10" | 12" | FoldOut | Slip | $36.80 | |
| 20"×12" | 16"×10" | 14" | FoldOut | Drive | $44.50 | |
| 20"×14" | 16"×12" | 14" | FoldOut | FoldOut | $52.30 | |
| 24"×12" | 18"×10" | 14" | FoldOut | FoldOut | $56.80 | |
| 24"×18" | 18"×14" | 16" | DoubleFoldOut | FoldOut | $72.40 | |
| 24"×24" | 20"×18" | 18" | DoubleFoldOut | DoubleFoldOut | $98.50 | |
| 30"×18" | 24"×14" | 18" | DoubleFoldOut | DoubleFoldOut | $108.20 | |
| 36"×24" | 24"×18" | 24" | DoubleFoldOut | DoubleFoldOut | $145.00 |
Custom Duct Transition Fittings — Smooth Size Changes
Duct transitions are tapered fittings that smoothly change the cross-section of rectangular ductwork from one size to another. Each transition is fabricated as four trapezoidal panels joined at the corners, creating a pyramid-frustum shape that guides airflow through the size change with minimal turbulence. Both the input and output dimensions are fully independent.
Reducing vs. Expanding Transitions
Reducing transitions narrow the duct to increase air velocity for longer runs or to match equipment connections. Expanding transitions widen the duct to slow air velocity, often used at plenums or before registers. ASHRAE recommends a maximum taper angle of 15° for reductions and 7° for expansions to avoid flow separation. Our configurable length parameter lets you achieve any taper angle.
Joint Types for Transitions
Raw edges are unfinished for field attachment. Slip and Drive joints allow quick mechanical connections. FoldOut creates a single-fold flange for bolted connections, and DoubleFoldOut creates a reinforced double-fold flange for high-pressure and large-format applications.
Common Transition Applications
Trunk-line step-downs are the most frequent use—reducing a 14"×10" trunk to 12"×8" after a branch takeoff. Equipment connections often need transitions to match the plenum outlet size to the duct run size. Our custom sizing eliminates the field cutting and taping that degrades system efficiency and increases air leakage.
Frequently Asked Questions
What is the difference between a transition and a reducer?
A transition can change both width and height independently in any direction (larger or smaller). A reducer is optimized specifically for narrowing the duct in one direction. Both are tapered fittings.
What taper angle should I use for duct transitions?
ASHRAE recommends a maximum of 15 degrees for reducing transitions and 7 degrees for expanding transitions. Our configurable length parameter lets you achieve any taper angle.
Can transitions be used for expanding duct size?
Yes. Transitions work in both directions. Set the output dimensions larger than the input for an expanding transition. Use a longer length for expansions to keep the taper angle below 7 degrees.