Park Tool - mini tool set...
 

comes with the following list of tools:

Includes CT-6 Folding Chain Tool, TL-1 Tire Levers, Double-Ended Spoke Wrench, #297 Open End Wrench (8, 9, 10mm)/, IB-1 Mini Fold Up Hex Wrench Screwdriver Set, GP-2 Pre-Glued Patch Kit, and TB-1 Tire Boot. The tools all fit neatly into a nylon tool wallet that slips easily into a jersey pocket or seat pack.

Can someone tell me what I would use the Open End wrench is for?

I am thinking this is for single speed hub or bolt-on wheels????

"The CBW-1 is an 8mm open and 10mm open end wrench. This small, nickel plated wrench can be used on brakes, derailleurs, etc. Hole in wrench allows easy hanging on peg board."