Unless my googling was horribly off, the Radiance's driver is the same one as the Elegia/Elear/Elex/Clear which all use the 40mm Aluminum-Magnesium driver. If there is any structural difference in the drivers, I can't find it. They're all more or less just different tunings, pads and minor cosmetic differences. Again, this is just what I can find on the internet. I only own the Elex, so I can't really pull another one apart and compare personally. They all still sound different enough, from what I've heard.
All of the Focal headphones aside from (sort-of) Utopia have the same cup shape. Same honeycomb mesh protecting the driver, same dimensions, and everything. They're cut from the same die, I'm pretty sure. All 3 of the closed-backs, Stellia, Radiance, Elegia, have very different looking backs on their cups, but that's just a different textured mold for that one piece.