Coupling for a fluid line system

Coupling for a fluid line system with a coupling part (1) into which an insertion section (5) of a counterpart can be inserted, and with a locking member (20) movably mounted on the coupling part (1) is mounted, and has a locking structure, in a arresting formed with a to the insertion section (5) complementary structure for locking the mating piece and the coupling part (1) cooperates with the locking member (20) having two parallel side portions (22, 23) is formed, wherein the coupling part (1) is formed facing inner sides of the side portions (22, 23) each have at least a longitudinally extending locking bar (24, 25), wherein in the region of the free ends of the side portions (22, 23) has a latching structure is provided, wherein the coupling part (1) having opposite guide grooves (13) is formed into which the Arretierstege (24, 25) engage, and wherein the clutch is steep (1) in the region of one end of the guide recesses (13) equipped with a to the locking structure formed complementary locking structure, characterized in that the coupling part ...