I was working on my buddy's Santa Cruz Stigmata and trying to take off his handlebars when I found the bolts on his Ritchey C260 Superlogic stem were corroded from sweat and the 3mm allen bolt head stripped. You can actually use another tool that will fit in the 3mm allen head.

This will work with any 3mm Allen head such as the ones on your derailleurs or front derailleur hangers.