The onyx chair is a fresh contemporary office chair that offers a range of inspired features such as height adjustable headrest and height adjustable arms independent back and seat tilt and contoured foam seat and back for extra support and comfort posture chair approved by a uk chiropractic doctor posture chair approved by a uk chiropractic doctor independent back andseat tilt contoured foam seat and back for extra support and comfort height adjustable arms adjustable headrest measureme