I wanted a quick way to test the smoothness of my prints and a quickly check for retention or coasting. If the print is not smooth enough to put the two parts together, then first adjust the temperature, then fan speed, finally adjust flow.
When your done use it as a fidget stick. Well its a little more fun than a cube.
Any PLA PETG
I found Ferjerez's Expansion / Flow Calibrator however, the diameter of both pieces where the same and would not fit without under extruding the pieces. I design my own pieces in Tinkercad and added a center hole to also test for retraction.