400 ton-class ammunition ship
|Class and type:||400-ton class|
|Displacement:||400 long tons (410 t)|
|Length:||54.875 m (180 ft 0.4 in)|
|Beam:||9.2 m (30 ft 2 in)|
|Draught:||3.2 m (10 ft 6 in)|
|Depth:||4.1 m (13 ft 5 in)|
|Propulsion:||6300ZC marine diesel engines, 600 hp (447 kW)|
|Speed:||11 knots (20 km/h; 13 mph)|
|Range:||1,500 nmi (2,800 km; 1,700 mi)|
400-ton class ammunition ship is a class of naval auxiliary ship currently in service with the People's Liberation Army Navy (PLAN). The exact type of this class remain unknown as of 2015, because no official information has been released, despite the ships have already been in service around a decade. 400-ton class is the most commonly referred term when describe these ships  400-ton class ammo ship in PLAN service is designated by a combination of an alphabet followed by three-digit number. The alphabet is Y, the abbreviation of Yun, which is for the Chinese character (运), meaning transport. However, the pennant number may have changed due to the change of Chinese naval ships naming convention.
Type 400-ton class ammo ship is the result of the need of a replenishment ship that can supply ammo at the sea, because the first generation Chinese replenishment oiler Type 905 Fuqing class lacked of the capability to supply ammunition, so ammo ships are needed to work in conjunction with Type 905 and other replenishment oilers. However, the small size of the 400-ton class limits it to the coastal waters, so in order to supply fleets much further out in the ocean, larger ammunition ships such as Yantai class were needed by the surface combatants. As a result, only a single unit of Type 400-ton class ammo ship was built.