China's stock index futures closed lower on Friday, with the contract for May, the most actively traded, down 0.54 percent to close at 2,172.4 points. The June contract went down 0.55 percent to end at 2,157.8 points. The September contract dropped 0.56 percent to end at 2,140.8 points, while the December contract lost 0.43 percent to 2,154.2 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.