China's stock index futures closed mixed on Monday, with the contract for April, the most actively traded, down 0.11 percent to close at 2,143.4 points. The May contract gained 0.02 percent to end at 2,133.6 points. The June contract rose 0.16 percent to end at 2,121.8 points, while the September contract went up 0.19 percent to 2,099 points. The stock-index contracts, agreements to buy or sell the Hushen 300 Index at a preset 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 was launched at the China Financial Futures Exchange (CFFEX) and started trading from April 16, 2010. The CFFEX has set the base value for all the four contracts at 3,399 points.