This is a more resin saving version of the Calibration Cube by iDig3Dprinting. It's made for SLA, DLP or LCD printers. It has the same size (20mm each side) and the axes are labeled for more convenience.
The bottom is open and drafted on the inside to allow good drain of the resin. Also there's a ventilation hole on the side as the top will normally be sitting on a print plate and not allow air to flow in.