I trust Brownell’s, and have for 25+ years.Late getting back to this... It was hard to be sure in the picture, but that was my guess as well. I find Rock Slide stuff to be a little crude and unfinished. I have a barrel and basically had to polish out burrs and edges. I'm all for supporting local, but...
If you get a refund and are looking at non-premium options, the Brownell's slides are pretty good. Rockey Brass has some interesting options as well.
Plus they have a no BS, forever return policy.