A model/ gender changer will allow SureFire E1 heads to fit Arc Flashlight battery holders:
This adapter above will work but the part should be re-designed
to pattern the SureFire thread/ O-ring configuration more closely.
The adapter interconnects SureFire E1 heads with the Arc Battery holders.
The SureFire Head is snugged on the adapter and the Arc battery holders serve as
a twist on tail switch.
Above and below, E1 and E1E heads are mated to Arc 123 battery holder.
Credit for this idea goes to Mr. Bulk of CPF fame. He conceived of this adapter to allow
for a double ended 123 battery holder; hosting an Arc LS head on one end and a
SureFire head on the other. The SureFire adapter combo is 5/16" longer than the Arc LS
head. A double ended 123 holder is no longer available but in the image below, the SF
head and adapter would replace one of the Arc LS heads shown:
Each light head has its own battery and can be turned on or off independently.
2 X AA battery lights for comparison (MiniMag -AA, Arc LS -AA & SF E1 on Arc AA holder using adapter