Well… I guess the title concludes it. The three parts are combined by one M3 nut and a M3 screw. Depending on which screws you have available you can use the parts for M3x12, M3x16 or M3x18.
One important thing to consider: The lower part of the z-adapter has a recess to leave room for one of the screws of the z-slider. The part must be inserted in such a way that the recess should point towards the front-inside.
The author remixed this model.