Sihoo Ergonomic Office Chair V1 4D Adjustable High-Back Breathable With Footrest And Lumbar Support Grey[Ergonomic design] The Y shape backrest frame of the ergonomic office chair provides all round elastic support and protection. The S shape backrest fits for the spine curve, and the global designed hand feel is as soft as human body shape. The ergonomic office chair provides long term comfort and perfect support for all health conscious users. [Customized high backrest] The 4D lumbar support can provide users with customized lumbar care. The 5 gear