Sihoo M57 Ergonomic Office Chair, Computer Desk Chair, 3D Adjustable High-Back, Breathable Skin-Friendly Mesh with 3D Adjustable Armrest, Lumbar Support 【ergonomic】 design recognized by the ergonomics application association for providing ergonomic designs based on extensive research conducted with digital models of the human body. The angles of the backrest have been designed for a near-perfect match to the human spine, lower seating pad includes thigh support for long sitting sessions. The results are a well-fitting chair that helps to dramatically release spinal pressure. 【premium】 materials the aluminium base is steady and durable while offering excellent resiliency against wear. Silent castors roll, rotate, and move freely without noise. Double-backed-frame design is sturdy and durable.