It fits 20x6x2mm magnet in the bottom so you can put it on some metal surface.
I incuded STEP file that you can change it as you can.
If you decide that you want to use the STL file make it a bit bigger. Instead of 19mm make it 22mm, or make it easier print the PLA or PETG g.code file.
I suggest print with supports on the bed.
(You will probably have to modify it a bit, but it was easy)
Happy printing!
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