A coupling for a fluid conducting system comprises an elongated coupling part (1) and a locking part (20), which can be displaced in a direction perpendicular to the longitudinal direction and which can be mounted on the coupling part (1) in a manner that enables it to slide. The guiding of the locking part (20) ensues via detent elements (24, 25) that engage inside guide recesses (13) of the coupling part (1). The locking part (20) can be fixed in a releasing position or in a locking position by the engagement of detent projections (26, 27) inside releasing recesses (18, 19) or inside locking recesses (16, 17). This enables a relatively problem-free operating of the coupling during opening and closing.