A total of 30 were built, initial boats being known as the Shanghai I class and later slightly improved boats being known as the Shanghai II class. Some boats even remained in active service well into the early 1990s. The Shanghai I class was slightly smaller than its successor, the Shanghai II class, displacing 125 tons instead of 135 tons, and had a twin Chinese Type 66 57 mm gun mount forward. All other specifications are identical to the Shanghai II class, which replaced the 57 mm with twin 37 mm gun mounts.