Hex wrench with 2 sizes (OPENSCAD, customizable), Ringschlüssel 7mm / 12mm

Updates 13.10. and 12.10.2015:
Version for Thingiverse Customizer, including additional parametric variables...

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1st Version 10.10.2015:
Small hex wrench with 2 diameters at the end of a handle. Parametric version, done completetly with Openscad.

Originally designed for 7mm and 12mm hex diameter to handle the nuts of my quadcopter, but hex sizes can be adapted to other diameters as well.

The size of the wrench key can be written as text onto the handle, this req