The Type 4 Offensive Unit was a type of Culture warcraft custom-designed and built by the GSV Sleeper Service in the decades prior to the encounter with the Excession near Esperi.[1]
It was based on the Killer-class Offensive Unit and had greater speed. 12,288 were manufactured and all were AI-cored and semi-slaved to Sleeper Service.[1] As a result, the fleet of warcraft manufactured by the Sleeper Service, including all other vessels of Types One through Six, were only capable of being used as a single unit, rather than a distributed war machine.[1]