This is a simple wind-up key with inner diameter 4x4mm for square shaft. The key features a comfortable butterfly-shaped grip with two finger holes, making it easy to turn and apply torque.

The model is compact, easy to print, and works well as a replacement key for wind-up toys or small spring-powered mechanisms. Thanks to its simple geometry, it prints cleanly on most FDM 3D printers without supports.

Perfect for makers, toy repair, or creative mechanical projects.