Belleze Office Chair Mesh Back Arm Rest Tilt Lock, Black Mesh back chair; ergonomically designed high back for the natural curvature of a person's back Tested & Certified - Meets or exceeds all ANSI/BIFMA standards Pneumatic gas lift system comes in the form of the lower handle The height adjuster handle also acts as a tilt lock, locking in the upright position Seat Dimentions 18"(W) x 19"(D) ; Back Dimentions 17"(W) x 20"(H)