What is this?

Eleiko were first to bring one out I think, and called it an “open” hex bar.

I have a Blk Box one, and aside from being able to do some single leg movements with it, as Cilian said, the other big advantages are it is easier to store than a full hex bar and it can be stood on the legs for loading and removing plates. Both compelling reasons to pick one over a regular hex bar.

A complete guess, but maybe for upright rows?

Yeah, it's weird. I guess it could be a kind of cambered bar curl, but as we've both concluded, it seems like upright rows are the most likely.

That's one of the strangest mini bars I've seen, but it won't be the last.

Hmm. But aren't the handles on the outside orientated the wrong way for it to work as an ez curl bar? I can see how you could do reverse curls that way, but I can't see how you could use them for normal ez curls.

This really is the worst design ever. Even if you did want to do hammer grip type curls there are shortie multi-grip bars that are far better designs.