Original LEGO® bricks are cast from relatively soft ABS plastic to an accuracy of a tenth of a millimeter. 3D printed bricks, on the other hand, are generally harder and have small irregularities or inaccuracies depending on the printer. Depending on the material, the brick also contracts to varying degrees when it cools. It may therefore be necessary to adjust certain parameters individually in order to achieve a high accuracy of fit.

The 3D printed calibration tool helps to find the settings for a perfect fit. The tool can be used to find the optimum values for knobSize (the diameter of the knobs), wallThickness (the width of the walls) and tubeZSize (the diameter of the vertical tubes). These three values essentially determine the fitting accuracy of the bricks.