This piece is for calibrating overhang and retraction settings on your 3D Printer. It has four overhangs (35, 45, 55, and 65 degrees) measured from the vertical with the numbers to be printed on top for reference. Each of the four overhangs is split apart far enough that it can be used to test the retraction settings of your printer. The ideal outcome is to not have any strings between the overhang towers and no droop under the overhangs.
We found our ideal settings to be 2.5mm of retraction at 40mm/s using Slic3r on Repetier Host. These settings are for the MakerGear M2.