Bought this add on for my Millenium ST-95 chair to hang the guitar from the back when done, and it fits it perfectly and is solid. You can adjust the height by moving it to a different hole and it doesn't move. It's great. The only problem is that when you hang a guitar without a square head, the guitar feels like it might fall off as the fixed space doesn't hold it perfectly on both sides, for obvious reasons. It's not that you can't use it, but it's safer with a square head.
Apart from that detail, this is such a great, solidly built add on and well worth its price. :)