A description is given of a method for ensuring the dimensional stability of pouring-out openings in or on a plastic container produced in an extrusion blow moulding process, in particular for calibrating said openings. This involves placing into a cavity (4) of a blow mould (1) a portion (20) of a parison extruded with one or more layers through an extrusion die and inflating it as provided by the enclosed cavity by means of a calibrating blow pin (11), wherein usually at least one of the pouring-out openings of the plastic container is predefined, in particular calibrated, with regard to its inside diameter and its inner contour. After that, the fully inflated plastic container is removed from the mould. In the case of the method according to the invention, all of the pouring-out openings (33, 35) of the plastic container (30) are calibrated substantially at the same time by the inserted calibrating pin (11). For this purpose, the calibrating blow pin (11) is formed as a double calibrating blow pin with two calibrating regions, and the double calibrating blow pin is inserted axially into the portion (20) of the parison once a head plate (5) of the blow mould (1) has been closed, but before the blow mould (1) has reached its fully closed position. A description is also given of a plastic container with pouring-out openings calibrated by the method according to the invention.