CaliCube

This is CaliCube, the calibration cube!
Unlike the other cube out there that is misguiding people to set the steps per mm of the x, y and z axis wrong, this one is for adjusting the flow rate on your slicing software.
Also it's not actually a cube...

Before you print this, you might want to check if your extruder steps per mm is well configured, but even if you don't bother to do that, it's alright, the flow rate is a multiplier of the amount of filament and the end result should be the same.

Print it with your usual slicing settings and measure it, preferably with a digital caliper. Don't measure near the bottom.
If it's measures are bigger than the labeled distance in mm (and smaller in the 12 mm internal distance), then you are over extruding and you should lower your flow rate. If it's smaller, you should raise it.
By how much? Try 10% per 0.1 mm difference and keep trying from there until you find it perfect.

The 16 mm height of the cube isn't affected by the flow rat