Replacement fitting for the pneumatic PTFE tube fittings that come with the  Ender 3 Pro.
The original version was non-manifold and ended up printing a layer in the middle of the tube running the length of the fitting. I imported and the STL into blender and cleaned it up, removing all non-manifold edges and overlapping faces. I also slightly increased the tube diameter as filament was binding when trying to swap to another spool.