The Ban Liang was the first unified currency of the Chinese empire, introduced by the first emperor Qin Shi Huang around 210 BCE. It was round with a square hole in the middle. Before that date, a variety of coins were used in China, usually in the form of blades (knife money) or other implements. The standardization of currency with this round coinage was part of a broader plan to unify weights, measures or axle width during the Qin empire. Ban Liang coins continued to be used under the Western Han dynasty until they were finally replaced by the Wu Zhu coins in 118 BCE.