I really love the way this chair supports my back. It's springy breathable and rolls well. The only problem I had with it is reading the setup instructions. The diagrams were pretty clear up until the last one which reads something like "To assemble chair sit on it" with a little arrow telling you to put the top half on top of the base. There's a knob on the chair just front of center with a hole big enough to look like the shaft of the base would fit into it but that's not where it goes. I ended up sitting on the chair to try to finish assembly with the shaft in the wrong place and nearly broke something - the chair or my neck! I'd recommend some better illustrations around this particular step.
The head rest can not be adjusted to go any higher. I have issues with my siactica. After 20 mins my legs got numb. On the second day of use the tilt tension stop working. That right there did for me.....I returned it. The only good thing on this chair is it offers excellent comfort on my lower back.