Professional tools at hobby prices are rarely what they seem, and that's the case here.
The adapters for different style watches, are cheap plastic and the mechanism which tightens and adjusts the tool, won't hold position so you are constantly trying to turn to loosen the back as you turn the adjusting knob. If you need to open a watch case a few times a year, this is frustrating but will eventually get the job done. For more constant use, forget it and buy better quality.