Fully-adjustable head Rest provides personalized neck and head support, adjustable lower-back lumbar support allows for free adjustment of both height and depth of support, 3D adjustable armrests can be adapted for different office applications with full 360° rotating handrails, 90°-120° reclining backrest adjustable for multiple work positions, Seat Height can be adjusted for 10cm (3. 9 in.) total vertical travel SIHOO office chairs have been certified by BIFMA and SGS, passed the 2000 lbs static pressure test. It can carry a weight of up to 150KG. Every part of this computer office chair has strict safety quality testing, cushion impact test, handrail fatigue test, chair foot static pressure test, ect. Simple instructions enable anyone to put a chair together in eight simple steps! High-grade materials the aluminum base is steady and durable while offering excellent resiliency against wear. Silent castors roll, rotate, and move freely without noise. The double-backed-frame design is sturdy and durable. The warranty period is two years. If there are any quality problems, please contact us. After confirming, we will provide a replacement part or product for you. SIHOO provides full parts coverage for the two years of the period, at zero cost for you!