In their marketing, Flexispot tends to throw around some buzzwords like “3D lumbar support” and “4D armrests,” but these boil down to basic adjustments that most office chairs have. The “3D lumbar support” just means the lumbar piece has three different height levels it can slide into. The “4D armrests” can be adjusted in four directions: lateral rotation, forward/backward, laterally left/right, and vertically up/down.
Other adjustments include the seat depth, chair height (via a Samhongsa Class 4 Gas Lift), the height of the headrest, and the aforementioned recline. These adjustments are easy to make (often just sliding or pulling the section until it clicks), and the pieces hold firm in place once they’re set.
There are some adjustments I sorely miss, though. First and foremost, the lumbar support is permanently attached. Flexispot’s focus with the Soutien seems to be posture, and the lumbar piece helps in that. However, I know that lumbar supports are not everyone’s cup of tea (myself included). Allowing the removal of the lumbar piece would greatly increase the flexibility of the Soutien, but I also understand it would make the lumbar support less firm and supportive.
Other options like the initial recline angle of the backrest (which is set firm at 90°) and the seat would also help the Soutien appeal to more people and feel more premium. As it stands, the basic adjustments (plus a few more) are present, and they are well-executed.