Non-main contracts can also be traded, but the trading volume of non-main contracts is generally small, and the trading will not be too active and intense. Sometimes things happen that you want to buy and sell but don't have enough counterparties at the right price, so generally everyone mainly participates in the main contract.

Master contract and non-master contract exist at the same time. As the expiration date approaches, the positions and turnover of a main contract will gradually decrease until the contract ends on the delivery date. At the same time, the trading volume and positions of forward contracts will increase with the passage of time and gradually become the main contracts.

The so-called main contract refers to the contract with the largest position. Because it is the most active contract in the market and the easiest contract to clinch, speculators are basically participating in this contract.

The difference between futures and stocks is that the life cycle of futures contracts is limited and will not be delivered until after the last trading day of the contracts. The so-called main contract refers to the contract with the largest position. Under normal circumstances, the contract with the largest position has the largest turnover. Because it is the most active contract in the market and the easiest contract to clinch, speculators are basically participating in this contract.