The legions of the late Republic were, structurally, almost entirely heavy infantry. The legion's main sub-unit was called a "cohort" and consisted of approximately 480 infantrymen. The cohort was therefore a much larger unit than the earlier "maniple" sub-unit, and was divided into six centuriae of 80 men each. Each centuria was separated further into 10 "tent groups" (Latin: "contubernia") of 8 men each. Legions additionally consisted of a small body, typically 120 men, of Roman legionary cavalry (Latin: "equites legionis"). The "equites" were used as scouts and dispatch riders rather than battlefield cavalry. Legions also contained a dedicated artillery crew of perhaps 60 men, who would operate devices such as "ballistae".