This is just some guy's apartment. He sells fixed-gear bikes on Taobao but you can also go down to his place to pick out parts and he'll build you a bike in a couple of days. They cost less than some of the trendy bike stores in downtown Shanghai. Prices start about 700rmb and hover around 1000rmb. He also sometimes has second-hand bikes. Call first to tell him you're coming, or contact him through his Taobao store.