OTTFF 8 Pcs 2020 Series Extrusion Profile Parts, Aluminum Alloy Flexible Pivot Joint 180°, Solid Connector Point Fittings Hinge, 3D Printer Accessories(Screws not Included)

These Items would get a much better grade except for a mounting problem. I tapped a 6mm hole at the end of the Extrusion and one side of the part mounts fine, the other side is too small for the screw head to go in between the wings. It will not accommodate a 6mm screw which is needed to tap the extrusion. A 5mm Button head screw will fit but will not tap a thread in the end. So, I used an old toolmaker's trick and mushroomed the hole on the aluminum extrusion with a ball bearing. This allowed me to screw in a 5mm screw. Now it's only holding in a small part of the extrusion but what I'm doing with it, it should be absolutely fine.

Quality is good, but, as others have pointed out, these can't be attached to the necessary M6 thread on the end of 2020 extrusion because the screw head won't fit. I tried round head "button caps" as well as socket heads, and neither fit. The latter is about 0.3mm too big. I'll probably try chucking the screws in a drill and sanding them down. Will look like garbage, though.

If the screw you use has a head that's too large it will interfere with the pivot. I've found that M5 and M6 screws are hard to find in a size that works, but these are the sizes necessary for use with 2020 rails that this is designed for.