These are two parts for repairing a window screen on my RV. They're used to connect the aluminum extrusions together. Getting the rounded corner piece was going to be difficult, and making the square piece was simple, so I just made them both. :-)
The rounded piece has a radius of 63mm. This is approximate to the original due to the original being bent and broken. It does seem to fit well, though.
I could add rounded pieces of other sizes, too, if anyone needs one. I just need the radius of the circle. If you take the original and draw lines from the flat edges, they should meet in the center of the circle that four of these pieces would make. The length of that line (from the outer edge to where the lines meet) is the radius of the circle.
I printed this at 0.1mm with three shells for strength.