I have these two. I've had the one on the left for a long time and it has a weird extra arm welded to it. 12ga hull is really difficult to pop in and out of it, but it's squeezes to a the 12ga size
The one on the right I recently picked up. It actually has a '12' on the sizing mandrel/piece. The hulls go in and out a lot easier and it sizes down to 12ga size as well, but I'm not 100% sure it would hit a low brass hull. Just seems like it might not, I haven't actually tested it because I could only find the one hull, the rest of my shotgun stuff is still in storage