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 comfortposture chair approved by a uk chiropractic doctordurable fixed armsindependent back andseat tiltcontoured foam seat and back for extra support and comfortheight adjustable armsadjustable headrest measurements seat height ndash 480 580mmseat