The seat and backrest follow the movements of the person sitting in a synchronised manner and at the correct angle. Infinite, immediately noticeable adjustment of the constant backrest counterpressure in all working positions (for body weights of approximately 40-125 kg). Patented automatic weight compensation for a permanent upright seated posture (Patent no. EP 06 35 228 B1). Synchronised movement can be locked in 4 positions (SD I). Option: infinite locking of synchronised movement (SD II). Integrated seat-tilt adjustment (up to -4°) during the movement process thanks to a seat that is divided into 3 sections (active pelvic support). Seat-depth adjustment using sliding seat (5 cm, can be locked in 5 positions) as a standard.