Thanks for response,
actually my object are a little more complex. Now I'm trying with some simple shape(like cylinder), but in future I want to import from some other software. At first I tried with .fbx format from blender. With ProBulider I tried, but have not good sense. But you know, for me is important to first have an object(imported), then create a cube around it, then get the subtract of these two object. I mean:
new_object = created_cube - imported_object. now my problem is the created cube is always smaller than imported object. I'm a little bit confused by the dimension in Blender and scale in unity. You can adjust dimension in Blender, but how in unity? By importing from Blender, the problem starts when you want to cover the imported object with an standard object from Unity!!They are not match together(I mean create by script)!!