Feeder vessels or feeder ships are medium-size freight ships. In general, a feeder means a seagoing vessel with an average capacity of 300 to 1000 twenty-foot equivalent units (TEU). Feeders collect shipping containers from different ports and transport them to central container terminals where they are loaded to bigger vessels, or for further transport into the hub port's hinterland. In that way the smaller vessels feed the larger liners, which carry thousands of containers. Over the years, feeder lines have been established by organizations transporting containers over a predefined route on a regular basis. Feeder ships are often run by companies that also specialize in short sea shipping. These companies not only ship freight to and from major ports like Rotterdam for further shipment, but also carry containers between smaller ports, for example, between terminals located on the north-west European seaboard and ports situated in the Baltic sea.