This simple cap is available with and without loop. It fits onto the banana plug pin to prevent short-circuiting or the introduction of foreign voltage during handling.

STL files are divided into looped and plain versions. They are further divided according to the size of the inner hole. M (4.3mm) should fit most connectors, but if the hole is too tight or loose, L (4.5mm) and S (4.1mm) versions are available or the model can be modified in the included SCAD file.