Modern Synchro mechanism, together with additional functions such as: sliding seat (in SL/SFLmodels), additional seat / backrest tilt (only in SFL models).
By loosening the screw you will decrease the reclining force, adjusting the chair to persons with small body weigh.
By tightening the screw you will increase the reclining force, adjusting the chair to persons with high body weight.
Grab lumbar support with both hands set it in the desired position.
Grab lumbar support with both hands set height in the desired position. By turning the knob left or right, adjust the pressure on the lumbar support.