Have an older Novatron power pack with the blue connectors for plugging in your flash heads? Novatron packs and heads now have a 6th pin. For the flash head to fit, the older units need the 4012 Adapter The black finish connectors don't need this adapter. Please DO NOT use this adapter with our new 2103-FC Fan-Cooled Bare Tube Head. It requires the packs with the black connectors