Topstar office chair Support SYinfinitely variable seat height adjustment with top lift, high contoured backrest with spinal column moulding, infinitely height-adjustable, intervertebral disc seat for optimum support in the pelvic area, synchro mechanism for synchronous adjustment of the seat and backrest tilt with body weight adjustment, infinitely lockable, PA star base black, load-dependent braked safety double castors, only suitable for carpeted floors, interchangeable with hard flooring, interchangeable with hard flooring.backrest tilt with body weight adjustment, infinitely adjustable, black PA star base, load-dependent safety double castors, only suitable for carpeted floors, interchangeable with hard floor castor set (not supplied), dismantled with assembly instructions.