EB means ExchangeableBond (abbreviated as EB), which is called "bond that can exchange shares of other companies". Refers to the corporate bonds issued by the shareholders of listed companies who mortgage their shares to the custodian. The main contract refers to the continuity of the main contract, that is to say, the main contract is the mechanical connection of all the main contracts to form a continuous contract, and the daily trading volume and positions are the largest, which will form a relatively continuous K-line chart. Which is the main contract.

The main contract is the connection of the main contracts in different periods, and the index is formed by weighting all contracts according to the volume. Obviously, there is a gap in the main contract because of the month change, and the index is the weight of all contracts, so there will be excellent continuity. In addition, the main connection must be completed within three months after the agreement is completed on the delivery date.