Two ultra-large 21,000-TEU container vessels built for Mediterranean Shipping Company were undocked and launched at Hengli Heavy Industry's Dalian facility in Liaoning Province. Each vessel measures 380 metres in length, 58.6 metres in breadth and 33.2 metres in depth, placing them among the largest container ships of their class. The two sister ships were constructed simultaneously in the same dry dock and undocked together in a single operation, a sequence that required careful coordination of hull block assembly, crane lifts and production scheduling. The in-dock construction period lasted 120 days, though this figure covers only the dry-dock phase and not the full timeline from steel-cutting to delivery. Both vessels will next move to the outfitting berth before undergoing sea trials and pre-delivery preparations. The ships run on LNG dual-fuel propulsion, powered by the 8G95 dual-fuel marine engine developed independently by Hengli Heavy Industry. Each carries a Type C bilobate fuel tank with a capacity of 13,000 cubic metres, built from specialised stainless steel and designed for compatibility with both LNG and liquid ammonia, allowing flexibility in future fuel choice. The tank is reported to be among the largest of its kind in the world. The launch represents further progress on the series of large container vessels Hengli Heavy Industry is building for MSC. As vessels grow larger, demands on propulsion, fuel storage and safety systems increase correspondingly, underscoring the complexity of the programme now underway in Dalian.