A medical tube set includes a tube and a stylet that improves the insertability of tube. The stylet structure comprises an inner core that can be inserted into the tube, an apical tip that is affixed to the apical end of inner core, and a movable expansion member that can move between apical tip of inner core and stop that is provided at a predetermined distance from apical tip. An engagement is formed at the posterior end of apical tip, and is able to engage the apical end of tube. By positioning movable expansion member within apical end of tube, apical end can expand radially outwards so that apical tip can pass through.
