Borg tactical cube

The Borg Class 4 tactical vessel was a type of heavily armed Borg cube utilized by the Borg Collective. The tactical cube differs from the standard Borg cube in several ways, the most notable being the extensive hull armor that covers a large portion of the exterior hull of the ship. The interior is also slightly altered from what is known of Borg 'architecture'. The vessel's central plexus is protected by multi-regenerative security fields.

Only one such vessel has thus far been observed by Starfleet - by the USS Voyager in 2376. The tactical cube was later caused to self-destruct by the Borg Queen during a brief civil war within the Collective.