It's a DSA "Enhanced Delta Ring", doesnt do anything special but the slab side looks good with the CASV
I love the rail system, think it's one of the most aesthetic ones out there. It does limit your optic options though since itll fuck any chance of cowitness unless you compensate for the raised rail over the receiver.
The pic in my previous post has a triji reflex sight that gets a lower 1/3 cowitness which is fine for me, this one has the Aimpoint T1 in the American Defense mount made specifically for the CASV so it lines up properly. I've heard other trijicons with super low mounts will work, could probably get an RMR to line up easily, but most optics will sit too high.
If you like the rail more than you dislike the inconvenience, its bitchin.