[Lockable Reclining Function] By pushing the handle up/down, it unlocks/locks the tilting of the back. This office chair feels great by tilting and locking the backrest to any situation you want, and 90-150° is comfy enough for you to work or rest in this mesh office chair for long hours. [Ergonomic lumbar support] The mesh backrest of this office chair is made of porous material to provide you with a breathable feel. The sturdy backrest frame supports the natural curve of the spine, allowing you to maintain a good sitting posture. The soft lumbar support pillow relieves the pressure on your lower back, and you can adjust it in 4 directions up/down/back/forth to make it more suitable for your lumbar, bringing more ultimate comfort.