The J-class was a type of freighter operated by the Earth Cargo Service in the early 22nd century. Ships of this type had a maximum speed of Warp 2, were equipped with shields and primitive inertial dampeners, and could transport up to 30,000 metric tons. Their warp drives were personally designed by Zefram Cochrane. (ENT episode: "Horizon") They were eventually superseded by the larger and faster Y class. (ENT episode: "Horizon")