There can be arbitrage between futures and spot, there can be arbitrage between two different delivery periods of the same commodity, and there can also be arbitrage between different varieties of the same series. As long as there is a relatively stable price difference between the two, when the price difference changes beyond the specification, arbitrage can be carried out.

For example, the ratio of A: B is generally stable at around 1: 2. When the ratio exceeds the specification and reaches 1: 2.5 or 1: 1.5, there will be arbitrage opportunities.