An extremely high quality tianium alloy clip kit originally made for NiteCore EX11 and IFE1 flashlights. It will also fit Jetbeam E3S light.
Note on the Jetbeam E3S: this clip fits very well into the pre-tapped holes on a Jetbeam Element E3S flashlight. It did require some widening of the holes in the clip (file them out a bit), and then provided screws fit perfectly. It's a nice springy clip with just the right amount of tension