A light-mass core was a type of power source for use in laser cannons. It was less than half a meter long and resembled a dull, metal rod.
D'harhan, a cyborg bounty hunter, utilized a light-mass core to power the laser cannon that was surgically attached to his body. Standard for his class of weapon, the light-mass core was shielded behind a protective interlock grid to prevent tampering. Removal was considered ill-advised, as such tampering could trigger an overload destruct sequence. In D'harhan, the light-mass core was situated within the cyborg's chest. Boba Fett, who knew of the nature of D'harhan's armament, was able to safely remove the light-mass core before the mission to Circumtore. D'harhan found the removal of the core to be extremely painful.