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It depends on the application. A 1/4 hollow is practically a wedge.. Best for heavy growth.

I know that TI makes some half hollows like this one:
http://www.classicshaving.com/catalog/item/846013/803567.htm

I thought there were some DOVO wedges around as well but I'm not 100% sure.

Usually thin grinds have lots of flex. However some full hollows can still be fairly substantial, so nothing's written in stone. I actually have this 6/8 full hollow G. Butler INOX that doesnt even...