Just reassembled my MPMD and needed to redo my dimensional accuracy calibration. I threw this one together because others I had been using were taking too long to print and were difficult to obtain accurate measurements.
This one prints pretty quickly but is quite thin so you have to be careful it does not flex when taking your measurements.
Make sure that, when you slice, it is oriented correctly on the bed. Each number corresponds to a tower so the resulting measurement relates to that particular tower. these are used to adjust M665 ABC (Rod Length Offsets) in M4MPMD.
Each of the outside measurements = 80mm (8cm) and the inside = 50mm (5cm) as indicated by the 5 and the 8 on the print.