Hinge guards to protect the paint on your door hinges from gravel road rocks.
Upper is slightly larger and will fit hinges with more rust/oxidation.
Lower is a tighter fit and will fit most hinges.
Updated tighter is more snug and slightly thicker. I had two of the lower ones fall off after 500 or so miles.
Latest version is the bulge. I checked this one against another JK and it fit well in winter. This is the one I now recommend using, do to the thermal expansion affecting the lower fitment.
They are designed thin to be cheap and fast to print, while still offering protection from rocks.
If requested I could make a thicker version.