SpiroFlex 160/125 reducing adapter (OC) nipple — concentric pipe reducer 160→125 mm

SpiroFlex 160/125 reducing adapter (OC) nipple — concentric pipe reducer 160→125 mm is a metal duct fitting designed to join circular ducts of different diameters while keeping the airflow axis aligned. The adapter provides a smooth, concentric transition from a 160 mm inlet to a 125 mm outlet and is intended for use in ventilation and exhaust systems in residential and commercial installations. Constructed to fit standard round metal ductwork, this concentric reducer helps maintain consistent airflow characteristics and simple mechanical connection between sections.

Advantages

The concentric design preserves the duct axis, minimising turbulence and pressure losses compared with abrupt or eccentric transitions. Manufactured for compatibility with round metal ducts, the adapter allows a secure slip-fit connection and can be combined with clamps, seals, or rivets for mechanical fastening. Its straightforward geometry simplifies installation and reduces the need for additional fittings where a concentric diameter change is required.

Suitable for

• HVAC ventilation ducts in residential buildings
• Commercial and light-industrial exhaust systems
• Air distribution networks requiring a concentric diameter transition
• Retrofit or repair work where a 160 mm to 125 mm reduction is needed

Key specifications

• Type: concentric reducing adapter (nipple)
• Inlet diameter: 160 mm
• Outlet diameter: 125 mm
• Material: metal suitable for ductwork (galvanised or similar finish typical for round ducts)
• Connection style: slip-fit concentric join intended for clamps, seals, or rivets
• Intended use: air ventilation and exhaust applications

How to use

Position the 160 mm end on the upstream duct and slide the 125 mm outlet into the downstream duct or fitting, ensuring the adapter remains concentric with the duct axis. Secure the joints using appropriate clamps, pop rivets, or duct sealant to achieve an airtight or mechanically robust connection as required by the installation. Check alignment and support the duct runs to avoid stress on the adapter and maintain consistent airflow. Follow local ventilation codes and manufacturer guidance for fastening and sealing methods.

Usage recommendations

Use the SpiroFlex concentric reducer where maintaining the central airflow axis is important and where a direct 160→125 mm transition is needed. For installations requiring reduced noise or maximum aerodynamic efficiency, ensure smooth internal transitions and avoid sharp bends immediately adjacent to the adapter. Inspect seals and mechanical fastenings periodically in commercial or high-use systems.