These finned stainless steel (AISI 321) REDAR “M”-shaped heaters are suitable for working in ventilated air. They have a specific load of 22 W/linear cm of finned tube. They consist of one element with d.10 in AISI 321 while the fin in AISI 304 is d.22 mm. These heating elements are suitable for the construction of high-power coils for heating gas in penstocks.