Looks like some steel RHS (Rectangular Hollow Section - of course the rectangle is square in this instance) to me. The centre piece looks like it was laser-cut. A bit of grinding required on the thinner bit I see, usually is the case with small, pieces from thicker material, especially with thin shapes, the laser just gets it too hot and it melts too much. If you are going to get one made one, get whoever cuts the little piece to do it from stainless, use parameters on the laser for stainless / ally (use Nitrogen) or use a water-jet / machining, for a nicer finish. Of course the amount of dollars goes up with each suggestion there lol. No offense to the poster who made his own, not saying it looks shabby, if it works, then it really needs no improvement.