Particle and Molecule are the boss of stage 7 from Streets of Rage 2. A palette swap named Oxygen appears as a mini-boss at the beginning of the final stage.
These robots are incapable of walking; moving around the level by hopping and jumping. The heads contain laser cannons that can shoot for long range attacks. When using the laser attack, the robots will kneel down to aim. Mid and close range attacks consist of launching spiked balls on a tether towards the player. They also have a area attack where they spin the spiked balls around themselves; forcing the player to keep their distance.
If the player moves in and grabs one of the robots, they will send an electric charge through it's body; electrocuting the player. Upon defeat, the robots self-destruct. These explosions can hurt the player.