Mesh back mesh material is very breathable which can prevent body heat and moisture. Iron frame with mesh on it can wholly support your back. Triangular pp chrome armrests stab fixed arms provide hours of comfortable support. Whats more, it can bear the weight of 150lbs. Heavy duty base with strong nylon casters chrome base can bear more weight than the plastic one. And the castors can offer you full range of motion and freedom of movement. So you can easily choose the right position for you.