I sharpen my saws using several different methods, including rotary tool where I would use these stones, so I have plenty of experience with them. The quality of these stones is very poor. The first stone literally broke off mid-length on the first tooth I tried it on. The second stone lasted about 10 teeth and then broke off too. When using the third stone, I had to go so light that I was hardly sharpening at all. After one 18 inch chain, the stone was so mis-shapened that it really was pretty much unusable again. I've used both Oregon and Forester brands previously and both performed way above these. I won't be buying this flavor again.