This is the lens ring from the d3wey FO-OSD (Fibre Optic On Screen Display).
Slides onto the the Hero3 lens and makes it possible to run a fibre optic cable to any status LED. It is available as a kit for the DJI Phantom (see other listings on my shop) or it is ideal for any DJI Naza based craft such as the F330, F450 or F550.
The video shows the full kit in action.
- d3wey -