Okay, I see. Looking at your hair, I'd say it's 4b.
And as for the crochet needle/hook, I understand what you are saying, but when I think of them, I think of a "standard" size, like one would get in a beginner's kit. I know they are different sizes. I mean, pen springs can be different sizes too depending on the pen (especially since they make those fat pens now that I love), but it's pretty clear to me what they mean. Furthermore, the NC definitions are not the standard end all be all of the hair typing defintions. I have seen other sites and info on hair types and the definitions can vary (a bit too much if you ask me) - once again why hair typing is subjective and irrelevant.