This is a customizable, fully 3d printable cord stopper for your backpack, sleeping bag or other nylon cord equipped stuff.You can download and customize the SCAD file itself or just use the customizer for standard tweaks of size, strength and number of circle springs (1 or 2) with or without grippy teeth on one or both sides, etc. The supplied .stl file is a pretty good size and configuration for general purposes and has grippy teeth on one side only. Take a close look at your sliced g-code before printing. For some reason KISSlicer (my preferred slicer) often wants to break up the circle spring paths in ways that would weaken them considerably. Slic3r seems to give better results, but not every time.