Originally posted by alex_96GL:

this is the one (craftsman 5" 15mm combo wrench va-47957):

so you see what happens: the outward arch of the lower side pushes on a sides of a bolt, rather than on the edge.
in theory at least. i don't see these wrenches in craftsman catalog anymore, so may be they were not that popular. I have mine and it actually works no worse than any open end



They're in my '05-'06 catelog, page 47...

2000 Mystique LS Duratec 2.5L MTX