The Emissary Paddle Shifter for SureFire fits nearly all holsters designed for X300 light-bearing handguns. Since there is such a massive market for holsters, we can't list every make and model. However, we can list holsters that can be an issue.
The Safariland 63 Series of light bearing holsters benefit from a small material modification to give the Paddle Shifter more clearance. This prevents the possibility of the Paddle Shifter getting knocked off during holster use.
Remove the overhanging material outlined in red with a file or dremel tool: