Summary

Fits a standard 12V socket to a 22mm handlebar for motorcycles. Diameter of socket holder is 29mm.

There's a cover when you leave the motorcycle outside in bad weather. Diameter 36,75mm, I had to print it at 99,5% to fit without falling off.

Let me know if you need a different diameter or a different socket-to-handlebar-angle (pointing more left or right if you wish, default is 30° off-center). Can rework as needed!