The Emissary Paddle Shifter for Streamlight TLR-1 fits nearly all holsters designed for light-bearing handguns. Below are details regarding specific incompatible holsters:
Most IWB holsters
Most OWB holsters
Safariland 63 Series light-bearing holsters require a small material modification to give the Paddle Shifter ample 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, or use a heat gun to move the overhanging material out of the way.