The Bionic FlexFit Backrest links 8 flexible panels through 14 dual connection points at the front, forming one support surface, while a dual-layer spherical bracket with 16 pivot points at the back lets it contour to your spine. On the electric models, lumbar depth is set by a motorized actuator controlled from the armrest buttons: adjust how far the support extends for a custom fit, or start an OmniStretch cycle with the third button. The chair is rated for up to 300 lbs (136kg under BIFMA testing; 110kg under EN 1335).