The Topeak Toolbar carries five bits in the slots inside, and I normally carry a sixth, a Torx T20 bit by Witte, a fine German supplier, for Rohloff use, just lying loose in the body of the Toolbar. Spare bits (there are several more supplied than will fit, or are required on my bike, which is designed from the ground up to use the minimum number of tools) are carried in the rubber/plastic holder, which can be carried on the Toolbar or on a keyring. Mine lies at home in the bottom of a toolbox.
In addition I carry an 8x10mm open-ended wrench, and that's the toolkit, which does for Rohloff emergency gear changing in case a cable breaks. In fact, I have an 8mm hex drive socket from another kit that will do the same job, but it's too bulky to fit inside the tiny Toolbar, yet too small to carry easily without losing it, so I carry the open wrench instead. The wrench is small and reasonably light, from a Draper bicycle tool roll. You can get the same effect by buying a good quality brake wrench and grinding it flat. (Park sells an 8x10 open wrench but it appears to be punched from flat steel; a piece of overpriced rubbish compared to the Draper item which will last a lifetime.)
On a world tour, of course, or even a tour less ambitious but further from a taxi than we Irish can ever venture on our small island, I wouldn't take the Toolbar, but a tool with all the bits firmly attached to the spine so as to be larger and easily recovered if dropped, indeed less likely to be dropped.
Andre Jute