This mechanism allows a coordinated movement of the back and the seat, with a ratio from 1 to 2,5, following the user's movements.
It provides a perfect support of the spinal column and the pelvis.
This mechanism can be locked in any position, and it must be possible to adjust the tension according to the user's weight.
Generally it includes an anti-return safety device which avoids a violent return of te backrest when the mechanism is released.
