Ningbo Tongkin Technology Co., Ltd. was founded in 1991 and has jurisdiction over Ningbo Dongjin Technology Co.,Ltd., specializing in the production of bicycle transmission systems, braking systems and other components. The leading products include a series of derailleurs, variable speed flywheels, high-end cassette hubs, disc brakes, brake components, cranksets and more than 300 varieties in six categories.

In 2015, in response to Made in China 2025, the company established Ningbo Dongjin Technology Co., Ltd. to develop a new internal and external variable speed transmission system, enteringechelon of the domestic industry. is the pursuit of quality by Richeng people. The company has introduced internationally advanced key technologies such as precision cold forging, CNC machining, heat treatment, and multi-station stamping to develop transmissions with Richeng characteristics. , transmission kit, sales volume leads domestic peers. The registered brands SUNRUN, TONGKEEN and HEMU enjoy high reputation in domestic and foreign markets. The company has independent export rights, and its products are exported to Europe, North America, Central and South America, Africa, Southeast Asia and other countries and regions. Xu Mingqiang, chairman of the company, sincerely invites domestic and foreign merchants to come for negotiation and guidance.