I don't actually use my Rex 121 mule and 15V fixed blades from Farid, though I've had them for years. I was searching for something else when I saw a post about SiC not working on steels above 4% vanadium, which didn't seem to jive with my memory. So I took out my Norton combo Stone from Home Depot and gave it a shot on the mule. I had a weak polish on the edge bevel back when I last played with the knife, though it wasn't sharper than paper slicing. The SiC scratched the edge bevel well enough, and then when I checked the edge, I was surprised by a meaty burr. I had to work at low pressure on both sides several times to remove it. Then I went to a vintage SiC/carborundum razor hone. That put a hazy polish on the bevel... and raised a small burr again. I chased that one down quickly, then stropped with 1 micron diamond on leather for no good reason because I hadn't really refined the edge. Has anyone else experienced such burring from Rex 121? I went ahead and did the 15V on waterstones after, finishing with 13k sigma power. Really minor burr formed at 1k that was easy to remove.