Excustive office chair with headrest and 2D armrest, chase back function with 7 gears adjustment, ti1. High back breathable mesh chair, wide headrest, mesh imported from Germany, elastic and breathable. 2. Ergonomic principle,BACK HEIGHT ADJUSTMENT This ergonomic chair control chairback height. double back provide better support, it can be adjusted in 7 gears. Lifting chairback with two hands directly when sitting. Lift each gear quickly to find a suitable height meeting your waist and back. Lifting to maximum height then go to lowest height in a