Since the beginning of the 2000s, a significant literature has developed around the study of the “revitalisation” of trade unionism. These contributions often take up typologies that oppose the ‘old’ and the ‘new’ and thus tend to harden the contours of what would constitute a ‘trade union renewal’. From this perspective, this article re-examines the nature and limits of this process, in the light of the Argentine case. It is based on a field survey of two comisiones internas that are emblematic of the ‘bottom-up revitalisation’ of Argentinean trade unionism since the 2000s. The localized and in-depth study of these two collectives makes it possible to document the concrete conditions of trade union work, by relating them to the socialization trajectories of the delegates and the social contexts in which they evolve. In this way, the article shows the constraints that lead delegates to internalise a ‘sense of limits’ in their work of politicising trade union action, thus highlighting the articulations between militant practices and service practices that characterise their modes of action.