Abstract: A captive cap for a screw-neck container, with a cap shell, a ring for the retaining thereof to the container, two articulable arms which at their forward extremities are linked to the cap shell and at their rearward extremities are linked to the ring, an upper frangible line extending circumferentially between 210° and 340° and defining a frontal separation between the forward extremities of between 150° and 20°, a lower frangible line extending circumferentially between 180° and 330°, where the lower frangible line comprises a recess located at the frontal separation and projecting toward the cap shell.