Felix's new FLX power cables with the Pollution Control Module.
"The 4-Plex above has something special inside. It's the new FLX Pollution Control Module that's designed to efficiently filter RFI and EMI-driven sonic artifacts. Installed inside the Hubbell, its range extends to all components plugged into its outlets. At this point, the Pollution Control Module will only be available as an option for the 4-Plex, but FLX Designs is actively working on other applications."