This design is based on the superellipse shape (https://en.wikipedia.org/wiki/Superellipse) which is a little bit more towards a rectangle, but still with the continues rounded shape.

It scales pretty nice, so if you want it a little larger or smaller, simply scaling the model before slicing works like a charm.

The smaller one of the print profiles (printed in gold PLA) is simply 70% of the larger one (printed in matte black PLA).