A device for dispensing flowable material through a flexible wall of a bag, comprising a sealing part provided in the bag, and a dispensing part provided outside of the bag, the dispensing part being adapted to be mated with the sealing part as it penetrates the bag wall to form a throughgoing connection sealed against the bag wall around the opening. The sealing part and the dispensing part include, outside of the areas surrounded by their bag sealing around the opening, cooperating interlocking means which upon mating of the parts engage between them and stretch the wall of the bag taut before the bag wall is cut, and which engage in an interlocking position at the end of the mating movement of the parts.