This compression plug is very well built and looks amazing. Like with any other compression plug just make sure the stem bolts are aligned with the compression plug so that it does its job properly. The fizik stem has the two clamping bolts too far away from each other so this plug can only support one of them, not ideal. One the Enve stem the bolts are much closer so it will work better.
A loose headset is not good. This plug fixed the issues on my bike. It holds the headset in place just like it should. I need to but another one for insurance, lol!!!