VR magnetic trigger for cardboard

I recently bought a VR headset to use with my smartphone. It act as a google cardboard with higher buid quality than a cardboard except it lack a magnetic trigger.

This trigger use the same magnet of the official google cardboard. Just put them inside the trigger and the back holder.
The back holder goes inside the VR headset. You will need to drill 2 holes (dia 3mm or 1/8") to screw the assembly together. It assemble on a flat surface.
You may also decide to glue it to the headset instead.