# Mirror not work correctly for stl imported file [duplicate]

I have a troubleshoot with my blender file. I've upload a stl file in blender and when i apply a mirror modify to X axis i see 2 objects. I tried to change 3d cursor position, but not work.

If you want so set the origin to a specific point, mark the point with the 3D cursor, where you want to set it. Then hit Ctrl-Shift-Ctrl-C and click on Origin to 3D Cursor.
One property of the Mirror modifier is called Mirror Object. Instead of mirroring the object at its own origin it will use the chosen object's.