【Features】SIHOO ergonomic chair with adjustable headrest can make neck tilt easily and comfortably, adjustable lumbar support bracket for free adjustment of height depth, 3D adjustable armrest for different office applications, 90°-126° arbitrary backrest adjustment for multiple work positions, any switch 3.15 in lift, 360 ° Freedom to rotate freely 3D handrail. 【Ergonomic design】SIHOO ergonomic office chair is recommended by Ergonomics Application Association. SIHOO's ergonomic design is based on the human body dynamic digital model. The ridge backrest and the human spine are exactly the same. The close fitting helps release the spinal pressure. The flow waterfall arc seating design Thigh support is comfortable, SIHOO will make you more comfortable. 【Mesh Material】The springy foam at the front end of the seat cushion and its curved design give you plenty of support while sitting. The seat and backrest are made of polyester mesh which is tough and breathable and provides support while keeping you cool and sweat-free on hot summer daysOur home office desk chair aluminum base is stable and durable, bearing quality is good. Silent casters move freely without noise. Double back frame design, stable and durable. 【Design】SIHOO is the crystallization of the common wisdom of many professionals in human body, physiologist, product designer, mechanical engineer,does its best to make every step comfortable and safe for every customer. Every small part has strict safety quality testing. Cushion impact test, handrail fatigue test, chair foot static pressure test, in line with the strict standards of office chair. 1. Adjustable 2D Headrest, 2D armrests, adjustable backrest, lumbar pillow, seat height. 2. Full-Mesh chair,Breathable and comfortable seat cushion 3. Noise free on different kinds of floor 4. Wide usage for work, study, releax, gaming 5. Pass SGS and BIFMA testing 6.enviromental material SIHOO series office chair packages: One chair with all parts; Installation tools; User manual;Pair of protection glove