I recently purchased 2 of these chairs for our office. One for me 5'10 and 1 for a co-worker 5'3 and this chair is a great fit for both of us. We both work for 9-10 hours per day and so far so good. We departed from the traditional foam seating since they have a tendency go flat after sitting for a long period of time.
This is a strong and great chair. The arms are adjustable height is adjustable with a lumbar support. The back lumbar support is fixed. The head rest can move only back and forward and cannot be adjusted once it has been attached. You can choose not to have the head rest attached to the chair. Everything is great with this chair the mesh back is firm enough to support your lumbar. However for me the Mesh seat back did not meet my specific lumbar needs and I had to return the chair. I could only sit in the chair for about 2 hours without any discomfort. Mesh seating is also strong but I my comfort level I find is with the padded or foam seating. Hope this information helps anyone interested in this chair.
Overall like the chair easy to set up easy to adjust won't be able to say much more without trying it for a long period of time (only used for about 1week so far). Will say that if you're over ~5'10" you will want to probably get a bigger chair (e.g. the similarly designed dexley if shopping at this price-point) or else be willing to go without the headrest. I'm 6'0" and went back and forth between ordering this or the dexley after reading lots of reviews. the consensus online seemed to be that the hyken was for people below 5'10" -- but all those reviews were also by "larger" people I am quite skinny so I was worried the dexley would be too large. In all respects the hyken fits me perfectly except the bottom of the headrest digs into the top of my shoulders and I had to remove it. (Before removing the headrest my wife also tried the chair and quite liked it - including the headrest but she's quite a bit shorter than I am.)