Small 35x35x35mm cube that can be used for calibration. (especially flow setting, cooling, retraction values, dimensional accuracy)-You can check whether all axes are aligned perpendicular to each other. Using the circles on the side. if oval, the alignment is incorrect.-Also, stringing or wet filament (as in my case) can be detected between the circles.-The circles also show how your printer behaves when there are overhangs.-The bottlenecks show whether the cooling is sufficient.- Bridging and the effect on dimensional accuracy is tested on the standing squaresThe cube is labeled so that all dimensions can be checked.-The two square blocks should fit into the 20x20mm recesses in the cube.In order to determine the tolerance for fits for your printer, the blocks have different dimensions at the top and bottom. If a side fits, the tolerance can be read.