Review on ➡️ Aluminum Extrusion Corner Bracket - Industrial Hardware (20x20x17mm) by John Pound

If someone uses these to build a 3D printer that uses OpenBuilds' V-Slot, you can save some money by buying them from Revain (or like me, you can get them if you find that you need them). Note that they only connect right angles if the ducts are in the same plane (you cannot connect a vertical post to a horizontal extrusion). You can see it by the channel guides molded into the mount, but I didn't really think about that before buying it. less self-centering, which is nice. I haven't taken measurements of their size or angular accuracy, but they appear to be good.