Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3447419.
Update [Feb 26]: I no longer add the nut above the thingi, because then the distance is depending on the tightness of that nut, which can be different between the two. I no just use an 20 mm bolt and either piece of plastic screwed in hand-tight, re-home, done. Getting very consistent results with the glass print bed. Unfortunately, not so much with the magnetic print bed; it appears my printing plate is hollow, deeper in the middle, where mosts prints are printed. So currently, printing exclusively on glass :)
While typing this I noticed the hole in the Glass washer being oval instead of circular. I uploaded a new version (v3) that has the smooth screw-hole. The original v1 version is not affected and because the V1 is tight around the bolt, it is the preferred version.
I created this thingi because I want to print on Glass as well as the magnetic build plate that comes with the Ender 5
I measured the magnetic (removable layer) 0.9 mm and the (Original Creality3D) Glass Print Bed that came with my Ender-3X at 3.8 mm.
So these two washers go on an M4x20 screw, followed by an M4x3 nut. When printed correctly, these washers should measure 3.5 mm for glass and 6.4 mm.
IN THEORY! this would eliminate the need to re-level when switching print bed. Just screw in a different thingi, re-home Z-axis and you're done.
Because of print-inaccuracy, you should print both in 1 go so they both have the same deviation. The point is they should have a 2.9 mm height difference, because that is the difference in thickness of the bed.
-- UNTESTED --
The rings are printing on my Ender-3 as I type this and I will make adjustments where applicable.
V1 has a tight screw hole V2 should have a smoother screw hole if needed, let me know, I'll upload a version with a 4.2 mm hole instead of a 4mm
Photo: a prototype with an aborted print, by chance a total of 3.5 mm thick, which is perfect for the Glass bed ;)