Used to test the accuracy of your printer and fine tune it to achieve perfect outside and inside dimensions of your prints.Read more about the process here:http://forums.reprap.org/read.php?262,407139,409002
These test pieces along with the Ultimaker guide on http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide let me get several problems with my Original solved quickly. Thank You!