The aluminum fin is formed from bi-metallic tubes, a base tube, and an aluminum muff tube. The fins are formed on a cold rolling process from the wall thickness of the aluminum muff tube. Extruded fin gives very good corrosion protection to the base tube, as the base tube is not visible to the atmosphere in between the fins.

The maximum operating temperature for the extruded finned tube is 300°C.

As a result, the tubes base is completely connected to the main tube. Since these fins never break, deform, or loosen, their heating efficiency does not change over time.