A bending sleeve is inserted between the pre-formed tubes which prevents wrinkling and buckling of tube walls during bending.  Longitudinal channels in the bending sleeve allow fluid passage between the tubes.

The sleeve is only required in bend areas, and remains inside the formed assembly providing support to the inner tube. Grounding spacers are used at tube ends to provide electrical bonding between tubes, as well as maintain tube concentricity at end fittings.

Wolfbend™ tubing under floor in passenger compartment