John, may be right about the panels being marketed under the Sunheater name in the US, but I would advise caution in making that assumption, while researching various panels for my solar heat project I found at least a couple of brands of panels that looked nearly identical, but were substantially different upon closer inspection, they both used the banks of flexible tubes like the one you are considering, and likely used the same 3rd party header pipe, but the tubing sections were made of different materials, and on company glued the tubes on while the other sonically welded them. (tube material for the other one was not compatible with sonic welding)
Ike