The bit that goes between the swing arm and the lamp head broke. This replaces it. I printed with 90% infill just for good measure, it may not be absolutely necessary.I printed with support in Slic3r, and a little cleanup is necessary - the large bit that inserts into the head needed a little sanding and the retention pin hole is only 2mm so I had to clean it up a bit before the roll pin would go back in.