It are three cubes into each other. Most angles are 45 degree. My Ultimaker had no problem with them. It took about 53 minutes to make and I scaled it to about 3cm in height.

This was my first object completely made in Blender. Blender is more complicated then Autodesk 123D but I have more possibilities and I can change more. Even .stl files I can work on. Great programm.