OM System PFCA-03 Optical Fibre Cable Adaptor

Underwater strobes are triggered optically, not electrically, because a wet electrical contact is a leak waiting to happen. The PFCA-03 is the fitting that lets a fibre-optic cable pick up the camera's flash through the PT-058 or PT-059 housing and carry it to an external strobe.

It is a small part that makes the difference between a housing that can only use the camera's own flash, which backscatters off every particle in front of the port, and one that can run proper off-axis lighting.