This is a tiny bed-level tester that I designed. I place one in each corner of my bed and one in the center, but this can be changed if appropriate for your needs.

This 20mm disk has segments that are one, two, or three layers thick. There is a sloped section in the middle with a hole. It is designed to be easily removed without damaging the thin parts. and for inspection of the first few layers.

I use a Monoprice Select Mini printer, so I originally designed it using the "Magic Number" layer heights. File "Bed_Test_0.2625_-_0.175.stl" is meant to be sliced with a first layer height of 0.2625mm, and remaining layers of 0.172mm.

I have also provided versions for 0.1mm ("Bed_Test_0.1.stl") and 0.2mm ("Bed_Test_0.1.stl") layer heights, as these seem common for most other printers. I have not personally printed them, but if you priter is capable they should work.