Neutrik SCDR is a soft plastic cover for the rear ends of several D-size chassis connectors.
Use it to protect the gap between connector and cable. It works with all common wires and cables – you simply cut off the cover end to the preferred diameter.
For PowerCON, it will help insulate the power, to avoid any nasty surprises.
SCDR works for XLR, SpeakON, PowerCON, and just about any unified D sized panel mount you can find.