are you looking for a stone to sharpen your knives? or is "pro" a brand name?
the knife fanatics have a long shopping list of what particular brand / natural / artificial / grit "ratings" etc etc etc that goes by the steel used in the knife - so getting into the scary sharp realm it is not a real simple question...
I have a tri-corner stone from Sears, I think, I used for almost 30 years doing free hand sharpening - but my criteria for "sharp" is not in the same class as the knife nuts..... I only demand they cut with ease, as I don't use my kitchen knives to shave my face (g)