While I'm here, just a few more little tips:
1. The internal diameter has been drilled accurately and is obviously the same diameter all the way along the length of the tube. The guide posts, however, usually have a slight draft angle on them so they are bigger at the bottom of the shaft than at the top. You can adjust this misfit in two ways. One is to use some fine sandpaper to sand down the guide shaft; the easier way is to open up the bottom of the guide tube hole a little. This can be done with a taper reamer, or with a sharp X-Acto blade, or even a small round file. A taper reamer is a useful thing to have anyway, here's one version:
https://www.micromark.com/T-Handle-ReamerIn particular when using the Slot.it wood guides, this is needed. I would suggest starting with the 3.7mm tubes for that guide.
2. Since all the tubes look the same apart from the internal diameter, they are marked to identify them. The 3.7mm tubes have two small drill dimples at the top of the outer diameter, the 3.55mm versions have one dimple, and the 1/8" versions are plain with no dimples.
3. Not all guides have a tall enough post to reach the top of the tube, but it is easy enough to trim the post down with a file or a cutting disk in a Dremel tool, or even a small metal saw. I usually leave them as long as the body clearance will allow, to give as much support as possible.