The Sowell Class Armed Medium Freighter is pretty typical of the cargo ships running the space lanes. She’s big enough to deliver a seasons worth of supplies to an outbound colony, with her fusion plant and Type 3 Ion Engines she has the legs to make a long voyage in a relatively short amount of time. She has the weaponry to defend herself from any run of the mill ship jackers and a perhaps a single pirate ship.
The Sowell Class is 280 meters in length. Her standard crew is twelve, and she can run 8-10 months at a time without having to replenish reactor mass.
These mid-cap ships are the backbone of interstellar commerce. The big freight companies are usually too scared to head off the beaten path to the Outer Rim or the Outback due to piracy concerns. So, these smaller, more agile ships pick up the slack.