Stroke keeps getting thicker

[Kamran.nef]

Hi, I'm trying to make flag maps but every time that I set the stroke on 0.5px(I tried different widths) after saving the stroke gets thicker. I used 'save a copy' and use the following settings(as said in wikipedia)and these are the results

in the first one the stroke supposed to be 0.5px but it keeps getting thicker upon saving an opening.

Thanks

[Monika Gause · Accepted solution]

Somehow Illustrator doesn't write the unit into the file, which then might cause the issue.

Are you saving your work file as an SVG?

That would be a bad idea. Your work file should always be AI - the native file format of Illustrator. When you're done, export an SVG.

[Kamran.nef]

I need it for final product and exporting causes some problems. In some maps it changes parts of a border to circles. That's why I'm avoiding exporting. 

[Ton Frederiks]

Check the "Preserve Illustrator Editing Capabilities" as long as you are editing and (re)opening the file in Illustrator.x

[Kamran.nef]

But what should I do for final product? 

[Ton Frederiks · Accepted solution]

Export an SVG

Since you will have the .ai file you can always make changes and export again.