1 Import
1.1 The mesh is screwed, invisible or scaled odd
Possible cause:
1.1.1 The object is scaled
When exporting the object the global scaling of the object should be set to {1.0, 1.0, 1.0}.
This happens if you scale the whole object within the object mode in Blender. You should apply scaling only in the edit mode. If you want to scale the whole object, press [Ctrl]+[A] and scale.