New backrest concept with unique freedom of movement. High, contoured backrest with spine shaping and lumbar support, waisted backrest shape for maximum arm freedom, height adjustable via grid mechanism. Special intervertebral disc seat for optimum support in the pelvic area. Synchronous mechanism for synchronous adjustment of the seat and backrest tilt, spring force adjustable to body weight, infinitely lockable. Black polyamide base, equipped with load dependent braked safety double castors for carpeted floors. This model bears the GS mark of the LGA Nuremberg and fulfills all safety-relevant requirements in this context.