I needed a set of basic calibration cubes. Others do exist but these are all in one place along with an extruder calibration chip - print this out in various materials to check extrusion flow, retraction settings and also temperature. The Extruder calibration chip has a number of common features on 3D models, including a small bridge section and various slopes. Check these printed features along with a test fit for a standard 3mm nut. Finally you can also store a short section of 1.75mm or 2.85mm filament at the side of the calibration chip, these chips can be stored in sets of material types etc. I hope you find it useful. I have included high resolution images so you can check my prints - they were all done on a stock Original Prusa i3 MK2 3D printer, with standard 0.4mm nozzle. They were sliced with Slic3r (Prusa version).