A system for mixing the contents of a first container with the contents of a second container. The second container has a port assembly for receiving the first container. The port assembly has an actuator that is constructed to access the cavity of the first container during activation of the system and to allow fluid communication between the first container and the second container. The port assembly further includes a movable plug that provides a seal for the second container. The plug is configured to move axially relative to the actuator during activation of the system, thereby opening the seal of the second container and providing fluid communication between the first container and the second container.