Cube for testing and calibrate 3D printer

Eng:
I don't know if there're similar designed before.
I like to use the tiny cube to test and calibrate my 3D printer.
Dimension: 20x20x20mm. There're through hole.
Pros.:
- Small so you'll get result fast (few minute)
- Can use to calibrate dimension
- Can use for test bridge printing
Con.: If you want to calibrate dimension more accurate, you must print bigger.
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Vie:
Dùng để kiểm tra và hiệu chỉnh máy in 3D.
Kích thước khối hộp 20x20x20mm, có một lỗ xuyê