Star Trek: Every Borg Ship Explained
1. Cube
As mentioned earlier, Cubes are the most common starships used by the Collective. Their simplistic design and gigantic size strikes fear into anyone unlucky enough to encounter one.
Their size is just over 3,000 metres across on all sides (giving them an internal space larger than 27 cubic kilometres), with a crew complement anywhere from thousands of drones to hundreds of thousands.
A Cube was the first Borg vessel encountered by Starfleet in the Next Generation episode Q Who (although the Borg were observed by the USS Raven years earlier, but these findings were never officially published). The Enterprise-D was unable to identify the ship's weapons or differentiate any parts of the ship. This is because, in a Borg Cube (and likely all other Borg ships), main systems are spread out across the interior, which, combined with their ability to quickly regenerate damage, makes them very difficult to disable.
The main purpose of Borg Cubes is assimilation, usually by locking onto a targeted ship with a tractor beam that slowly drains their shields. The interior space is big enough to hold the crews of multiple starships after assimilation is complete.