It's a gimmick, just about worthless on a modern bike; you're unlikely to get it in anywhere that you want to use it. Instead, if you can't source the Draper bicycle-specific 8x10mm spanner, buy a small brake spanner at a motor factor, getting the one with 10mm one side, 8mm the other side, and grind it flat to save weight. That lets you tighten up the only two nut sizes that should be on a modern bike (at the fork and on the rear triangle for fixing mudguards and lamps, and on the Rohloff for emergency gear changes).