SunRun is the component brand of Ningbo Sunrun Industry & Trade Co. Ltd. based in Ningbo, just south of Shanghai. Eerily similar to Saiguan (the two companies also have similar addresses), the company was founded in 1991 and claims to manufacture a mere 6 million rear derailleurs per year.
Like SunRace, SunRun have maintained the fine tradition of spelling their name in a number of different ways. As with SunTour and SunRace, you can find references to Sunrun, Sun Run, SunRun and SUNRUN. I have plumped for SunRun, as I consider that, if you are going to imitate SunTour and SunRace, you should do it properly.