A tube head assembly includes a tube head that includes a solid insert forming a lid closing the neck, a cap that includes a punch, and a removable spacing ring disposed against the shoulder around the neck. The ring and the cap are formed integrally in one piece and are joined by material bridges and configured in such a way as to allow sliding of the cap through the ring after breakage of the material bridges, characterised in that the ring includes internal stops adapted to limit the movement of the cap through the ring in such a way as to keep the punch spaced from the lid when the cap is screwed onto the neck and butts against the ring.