This kit includes one leather pump cap, one metal nut, and one plastic cap. These parts sandwich together inside the pump so that the leather cap can create an air seal when pumped.
The metal nut (the piece with the triangular opening) fits below the leather piece closer to the inside of the lantern, while the plastic part fits above the leather piece.
Note that the leather cap will need to be oiled before use, which can be found as part #: 200K2251 (not included).
To replace pump cup:
1) Remove spring clip.
2) Remove pump cup and metal plate.
3) Place plastic backup plate, collar forward, on plunger shaft.
4) Place pump cup on plunger shaft.
5) Replace spring clip.