The Shanghai Shenzhen CSI 300 Index is a stock market index that tracks the performance of the 300 largest and most liquid stocks traded on the Shanghai and Shenzhen stock exchanges. It is a free-float market capitalization-weighted index, meaning that the weight of each stock in the index is determined by its market capitalization. The index is designed to reflect the performance of the Chinese A-share market, and is widely used as a benchmark for Chinese stock market performance.