the hull of the original Type 021. Although the design was successful, more capable missile boats such as the Houxing-class missile boat were already becoming available, so the Houdong class was geared for export. Iran is the first customer and the one in Chinese inventory is used for training foreign crews, and as a demonstrator to other potential customers, as well as other test and trial purposes. References Missile boat classes Missile boats of the Soviet Union Missile boats of the People's Liberation Army Navy China–Soviet Union relations