Asynchronous mechanism with double forward pivot and anti-shock system, 20° inclination of the backrest and 9° inclination (+4° ÷ -5°) of the seat. Thanks to the activation of a clutch and a gear, the seat and the backrest can be adjusted separately. When the gear with the anti-shock system is left open, the backrest takes on the function of permanent contact and can then be locked in any of the 6 positions. The seat can be locked in any position available through the seat clutch. The tension of the backrest can be adjusted through a knob located underneath the mechanism.