This is a modular twist-lock connection system. It has a male and female end that can be inserted into any 3D model.
There are two versions:
My original purpose is to use these for designing modular, customizable lightsaber components (like in Jedi: Fallen Order), but I thought that the connectors themselves might prove useful to some. If your printer has even halfway-decent bridging, you should be able to print with no supports.
Includes STEP and STL files.