That circumference description is so misleading. I crochet, and they are crochet hooks, for one. Second, and more important, I have hooks that vary in size from 3mm to 16mm... That's a very large difference! So, which size hook are they talking about?
And, what is this Z pattern coil they keep referring to? My hair has a round coil pattern, no sharp angles. Yet has no definition. So, I'm not 4A, because I have no definition, and I'm not 4B, because I have no Z pattern. So, where does that leave me?