A light-mass core functioned as a power supply for laser cannons. These cores, used in laser cannons, were typically under half a meter in length and had the appearance of a matte, metallic cylinder.
The cyborg bounty hunter known as D'harhan employed a light-mass core as the energy source for the laser cannon that was surgically implanted in him. As was typical for this kind of weapon, the light-mass core was secured behind an interlock grid for protection against unauthorized access. It was strongly discouraged to try to remove the core, as this could set off a self-destruct overload. D'harhan's light-mass core was located inside his chest. Boba Fett, being aware of the specifics of D'harhan's weaponry, managed to extract the light-mass core safely prior to the mission on Circumtore. The experience of having the core removed was excruciating for D'harhan.