A device (1) is proposed which consists of a pouring nozzle (2) with a cylindrical circumferential wall (20) and with an internal thread (21) and a terminal flange (22), into which an adapter (3) can be screwed. The adapter (3) has an inlet end (30) with an external thread (32) and an outlet end (31) with a conical tube attachment (35). At least one combined perforating and cutting tooth (34) is formed integrally on its lower edge in the screwing-on direction. In order to achieve as high a sealing force as possible between the tubular bag (4) and the adapter (3), a special seal is proposed. To this end, the cylindrical circumferential wall (20) above the terminal flange (22) is guided into a double-walled region. The outer region forms an obliquely outwardly directed conical supporting-wall region (24) and the inner double-walled region (23) is formed by a likewise slightly conically designed but inwardly directed sealing skirt (25). Liquid which possibly tends to penetrate into the thread region while the sealing film is cut open is thus held back.