BEIJING, June 23 -- China's key Hushen 300 index futures opened lower on Tuesday, with the contract for settlement in July, the most actively traded, down 2.52 percent at 4,597.

The contract for settlement in August opened 2.71 percent lower at 4,588. The September contract lost 2.99 percent at 4,580. The December 2015 contract opened 2.7 percent lower at 4,608.8.

The stock-index contracts, agreements to buy or sell the Hushen 300 Index at a present value on an agreed date, are designed to allow investors to bet on and profit from either gains or declines in the market.

The index futures were launched at the China Financial Futures Exchange and started trading from April 16, 2010. The CFFEX has set the base value for all the four contracts at 3,399 points.

The Hushen 300 Index samples about a fifth of the total stocks listed on the Shanghai and Shenzhen bourses.