This rating is for 10an and 12an rulers. I've used 6 and 8 from this manufacturer with no problems. But 10 and 12 how difficult to collect them. It is not possible to wind up the leash, cut it and insert the end of the leash into the fitting in the form of a purchased ID. It wears out and there just isn't enough room to put the fishing line in it. I ended up finishing each adjustment about 0.04 oversize and everything worked flawlessly. Not everyone has access to a milking machine or lathe so I'm not giving 5 stars. But value for money? Excellent compared to going to the place to correct my lines. A drill press with a decent vise will also help.