The boats have received major upgrades and numerous refits since commissioning. They have six torpedo tubes and carry 20 torpedoes. Alternatively, they can carry 36 mines in their tubes. It is capable of firing sub-launched variants of the C-801 anti-ship missile as well as a range of indigenous and Russian torpedoes or mines. All remaining hulls have been refitted with new sonars, with Type H/SQ2-262B sonar manufactured by No. 613 Factory replacing the original Type 603 sonar on board. Anechoic tiles were added later to reduce noise levels.