B2 Super Battle Droids are heavily armored versions of B1 Battle Droids.
B2 Super Battle Droids were first built on Geonosis after the failed invasion of Naboo. Their heads were fixed on their torso. They were also dumber than normal droids. They had armor that was resistant to laser blasts. They took three shots to destroy. They had wrist blasters (commanders had rocket launcher arms). They were used in heavy assaults.