The C8's larger head size makes it less convenient for helmet mount, but it also means better heat sinking, and more throw and tight spill spill pattern due to the deep reflector. It uses one 18650 battery.
Best use scenario...
Much smaller and convenient than a D cell Mag light - good duty light for hip carry in a holster.
The C8 has a tight throw beam for reaching longer distances. Below are a few beamshots for comparison purposes, what you cannot tell is that the C8 throws more light for a further distance than the SL6 (which has more flood).
Convoy C8 w/T5