Just to review, and make sure you know what I'm referring to, today we have naming of parts. In the photo, I've labelled the cap, tip, tip holder, ink valve, and pen body to make the rest of this a little easier.
Also notice which end of the valve attaches to the pen body. And pay attention to the little ball inside the pen body. If you have a different sized pen, it may be a different color. Don't let this alarm you.