A piercing fitment assembly for a thin film flexible container containing a liquid having(A) a spout assembly having a sealing flange sealed to the film of the flexible container and having positioned therein a circular piercing element with at least one piercing point in close proximity to the film of the flexible container；(B) a threaded plug fitted into the spout assembly and the bottom of the plug being sealed to the film of the flexible container；(C) a threaded collar positioned in the spout assembly and threadably engaged with the threaded exterior of the threaded plug；whereby when the threaded collar is moved to engage the threaded plug and the threaded plug is moved away from the film of the flexible container, the film of the flexible container is brought into contact with the piercing end of the piercing element and the film is pierced allowing the liquid from the container to flow out through the spout assembly and out of the flexible container.
