I recognised where it came from , and I really like the F1 USB solution, and now I started wondering how it was done. It took a blowtorch and some force to find where the head/battery tube joint was:
So they extended the head part a bit compared to other tube flashlights, and the driver sits lower,to make room for the USB socket. Which adds 8mm length to the F1 exclusively for the USB port which is not really needed. The cavity from driver to ledshelf is a whopping 22mm, they really made no effort to make the F1 compact.