Mandrel bender - GIF

[old kodger]

That is the mandrel. Some are bars with a shaped end that finishes at the bend point, some are balls linked together and in this case disks linked together.
The object is to support the tube from the inside at the bend point to prevent deformation. This guy is doing a first class job, those bends are super smooth.

There is some sort of "goop" in there as well, you can see that it has dripped out onto the machine at 0.20.