The holes are different sizes: 4mm, 3.5mm, 3mm, 2.5mm, 3mm, 3.5mm, and 4mm (its symmetrical :D)

The model is best printed flat, rather than how it is oriented in the STL file.

You can edit the dimensions on inventor (if you have it).

I've been using it for a year now to stop my cables from falling through the hole in my desk.