"ji zi" is a trademark of glazed series chess pieces owned by Shuangyuan, which has the same vein as Yunzi and Yongzi crafts. According to historical records, in the Western Zhou Dynasty more than 2, years ago, the Central Plains had a process of making colored glasses, and then it was spread to many places in southern Yunnan through the Silk Road. Weiqi was popular in Luoyang, the capital of the Tang Dynasty, and it was a very popular cultural entertainment among the nobles in the palace, including many colored glass pieces. In modern times, Luoyang is the base of glass-making technology in China. After several generations of research by experts in glass-making industry in Luoyang, the ancient glass-making technology has been comprehensively inherited, improved and innovated in the dual chess industry. The sunspot is green and transparent, and the Bai Zi is as transparent as jade, with elegant color and warm and smooth feel, which is deeply loved by the majority of chess players.