Non-separable attachment for dispensing device

Metal housing provided with a sidewall and a neck connected to the sidewall via a shoulder, the neck being constructed and arranged for irreversible fixation to a dispensing head for perfect leaktightness to liquids,

• the dispensing head comprising a plastic flange provided with a sealing skirt and an outer catching skirt provided with a snap-fit rim on its inner surface, wherein the neck has a wall and the shoulder has a wall, both said walls being of substantially the same thickness as the sidewall,
• said metal housing comprising:
• an open end in the form of an orifice surrounded by a curl oriented outwards, the neck having a minimum inside diameter being equal to or slightly less than an outside diameter of the said sealing skirt;
• a first substantially cylindrical part;
• a substantially tapered shoulder connecting the open end on which the curl is formed to the first substantially cylindrical part;
• and
• a second substantially cylindrical part, having an outside diameter less than an outside diameter of the first substantially cylindrical part;
• the first substantially cylindrical part and the said second substantially cylindrical part being separated from each other by a shoulder that is located at a distance from the open end such that when the said flange has been fully force-fitted onto the neck, the snap-fit rim is urged to be folded down on a diameter smaller than the diameter of the first substantially cylindrical part.