I think the annoying thing about crochet hooks is they come in millimeters, letters, and numbers. So for example, the most commonly-used hook is the 5mm, but in the UK it's sometimes called a size 6 hook. But in the US it's sometimes called an H hook. What's aggravating is every hook I've seen always has just the damned millimeters, and usually they have the UK or US system on the side as an after note; it's usually patterns that rely solely on the letters and numbers. Instead of all this confusion, why not just have the millimeters?