pellmell No, what I'm saying is the Callaway Big Bertha and X series are both SGI. A thin sole doesn't automatically make the X GI.
Well now I'm curious. What are the defining specs that separate the categories, players blade, players cavity back, players distance, game improvement and super game improvement, and who sets the limits of each?
(I may have omitted some categories).
I know Golf Digest has their own when they review/rate clubs.