Summary

This will fit the Battery Holder/Controller for David Clark Headsets. Made to fit the DC One-X specifically, but I know it will fit the Pro-X and probably others as they appear to be the same form factor.

Fast print that slides in the groove on the side. It will allow you to operate the headset, yet cover the lights that are quite bright at night.

I suggest not trying to snap the clip over the controller, but to slide it on from one end or the other, then replace your hanging clip if you have one.