Duct Transitions & Connectors

Duct transitions and connectors bring HVAC duct runs together cleanly, letting you adapt sizes, shapes, and orientations without choking airflow. Whether you’re tying a round branch into a rectangular trunk or stepping from 10 in. to 8 in., the right fitting—reducers, increasers, round‑to‑rectangular transitions, wyes, tees, boots, collars, couplings, and offsets—creates a smooth path for air.

The payoffs are real: better airflow, lower static pressure, fewer leaks, quieter operation, and improved energy efficiency. Choose from galvanized steel, aluminum, stainless, or polymer fittings, along with insulated and gasketed options that limit condensation and noise. Profiles include beaded and crimped ends, slip‑and‑drive, S‑cleat/drive cleat, and flanged connections for quick, tight joints. Look for UL 181 listings and SMACNA‑compliant construction to meet code and withstand system pressure.

Picking the right connector starts with accurate sizing. Match nominal diameter or duct dimensions, check available clearances, and plan the transition length to minimize turbulence. Consider temperature ratings near furnaces or range hoods, and corrosion resistance for coastal or damp spaces. For bathroom fans, dryers, and kitchen ventilation, confirm appliance collar sizes and backdraft requirements. Mini‑split and rooftop unit hookups often need plenum transitions and vibration‑isolating flexible connectors.

Install with a “crimp downstream” mindset so joints are oriented with airflow. Seal seams and joints using mastic or UL 181 foil tape, and secure with sheet‑metal screws or rivets at proper spacing. Support longer runs with hangers, then pressure test or smoke test to verify tightness and balance dampers for even air distribution. Handy tools include aviation snips, hand seamers, duct crimpers, a nut driver or drill, pop‑rivet tools, and a tape measure. Wear cut‑resistant gloves and eye protection.

Shop our range of HVAC duct transitions and connectors to build reliable, efficient duct systems that deliver comfort and reduce energy costs on new builds and retrofits alike.

3-1/4" x 10" x 6" Galvanized Rectangular to Round Duct - 6" Diameter HVAC Transition for Microwave Exhaust Vent Kits & Duct Fittings
3-1/4" x 10" x 6" Galvanized Rectangular to Round Duct - 6" Diameter HVAC Transition for Microwave Exhaust Vent Kits & Duct Fittings

rectangular to round duct
3 1/4-Inch x 10-Inch to 4-Inch Diameter Galvanized Rectangular to Round Duct Transition Microwave Vent Kit Round Transition Vent Adapter for Connecting HVAC Range Hood Ducting Fittings
3 1/4-Inch x 10-Inch to 4-Inch Diameter Galvanized Rectangular to Round Duct Transition Microwave Vent Kit Round Transition Vent Adapter for Connecting HVAC Range Hood Ducting Fittings

4inch
6-Inch Diameter Galvanized Transition for Rectangular to Round Duct,3-1/4-Inch x 10-Inch to 6-Inch, Galvanized Round Transition Connecting HVAC Duct Pipe Fittings
6-Inch Diameter Galvanized Transition for Rectangular to Round Duct,3-1/4-Inch x 10-Inch to 6-Inch, Galvanized Round Transition Connecting HVAC Duct Pipe Fittings

B0DSW379VV
3-1/4" x 10" x 4'' Galvanized Rectangular to Round Duct Transition, 4" Diameter Microwave Exhaust Vent Kit Round Transition for Connecting HVAC Duct Pipe Fittings
3-1/4" x 10" x 4'' Galvanized Rectangular to Round Duct Transition, 4" Diameter Microwave Exhaust Vent Kit Round Transition for Connecting HVAC Duct Pipe Fittings

R-394