2mm diameter circular shaft (female) to Lego Mindstorms "x" shaft (male) adapter

This is a little piece of equipment that is intended for the purpose of connecting a 2mm shaft (e.g. of a DC motor) to Lego Mindstorms gears and wheels.

Please keep in mind that this is the first 3D model I have ever designed and I haven't even printed it myself yet. If it's not perfect, please don't be too harsh. I plan to print it myself soon, test it, and make modifications, if necessary.