These are hollow spheres, made of rubberized rocket fuel; when ignited, they propel themselves around at random at high speed, bouncing off the walls and breaking through doors, turning the entire building into an inferno. The makers call them "kinetic fireball incendiaries." The Pentagon doesn't want to talk about them, but published documents show that the fireballs have undergone tests on underground bunkers.
WTF!? Suffice it to say the Indiana Jones franchise would have ended 15 minutes into Raiders of the Lost Ark if the ancient Peruvians had employed a rocket ball instead of a giant freaking rock.
Click the article for a much longer explanation of the the weapons.
Thanks to 42 y/o undead warlock, who even giant flaming balls can't kill.