This is for a computer case I am making. The width is set for a 240mm radiator to fit in. The strength was great better than the other corners that had me concerned. Also much lower profile All it needs are the vertical and length tbeams of your choice. In my case I ordered 300mm tbeams for the length and cut 600mm beams to about 450mm for height.
Then I used 1/8th acrylic for side panels as it fits into the tbeam and secures it nice.
So I remade this ... the extrusions on the brackets actually did not work well, due to the tnut basically being flush on 1010 extrusions.