This ball corner is a quality part, with nice design to make it fit better with the case angle. Also with the big ball corner, the box bottom isn't laying on the ground, which is handy if it's raining or whatever.
The big ball corner does bring a small but, since stacking these atop another tends to be a bit tricky. Solution is of course the 4128 with the cup, but the boxes should be of the same size to fit neatly. I have been solving this by making the bottom corners with the 4128's and top with these. Then the bottom is more flat, and doesn't slide. Any how, quality parts.