Big and Tall Office Chair with Adjustable lumbar and slide seats , Headrest and 4d armrest , tilt function max degree is 115 °, 300LBS, Black1. Ergonomic design: Double Back Design. The lower back can be adjusted with the waist, which is called back chasing function. 2. The cushion can slide back and forth, allowing you to adjust a comfortable sitting posture, and relax the stiffness of your thighs and hips because of maintaining a posture for a long time. Seat cushion is made of molded cotton, which is comfortable to sit on and will not deform after sitting for a long time. 3. 4D armrest,