Ultimaker XY Axis Square

These little arms are a big help in squaring your 6mm shafts (that support the print head) to the perimeter 8mm shafts.

I added a small flat in the "V" end to allow measuring the length of the arm with calipers. I also usually take a utility blade to each end scraping (not cutting) lightly across the contact surfaces to knock down any outlier layers and bring them more inline with each other. You want very repeatable, even layers for this part to be of help. Mine measure within 0.02mm of one