Needle & hook size charts

I find myself frequently needing to know what size a 4 mm needle really is, or how big is a .75 mm crochet hook? Yes, I'm hopelessly lost when confronted with anything other than the American hook and needle sizing system. I do provide metric needle sizes in my patterns, for those in and out of the U.S. who use that system. At some point, I thought it might be nice to provide a chart of what the yarn sizes are, so that's here, too. These are they: