Rogerole; Black Magic sizes are the same as any Std hook. The B prefix designates that it has a 2XL Shank.
I think Black Magic is a Local Brand. http://www.fishingmag.co.nz/Black-Magic-Lure-Hooks.htm This link will allow you to have a look see at what the hooks are. Hope this is not taken as advertising. I have no connection with Black Magic other than I use their hooks for my Lake Flies. Have Fun. Jax