To begin with, it has the ever-important chain pin tool. I've been on some gnarly mountain bike trails that can brutalize any chain. And having that tool along means the difference of a ten minute pedal to the car and an hour-long (or worse!) hike.
Spoke wrenches are another often-trivialized tool, and this wrench has 4 of them. You'll be hard pressed to have a spoke that this wrench can't adjust. Which figures, because your buddy will break his odd-ball spoke and his cheap tool won't have the spoke wrench he needs. It happens.
(That said, it is NOT Shimano or Mavic wheel compatible. If you need those spoke wrenches you might want to look at the Topeak ALiEN III multi-tool)
Mountain bikers will be especially glad to see the T-25 Torx wrench for handling their disc brake adjustment needs.
Plus the most popular Allen wrenches (2, 2.5, 3, 4, 5, 6, 8mm) and 2 Box-end wrenches (8 and 10 mm).
Crank Brothers make several different versions of this tool, but this one is my favorite -- and the one we normally kept it stock -- since it had two different sized phillips and flat head screwdrivers. At only 7 grams more, well, it seemed worth the extra weight.
The frame for this tool is made from sturdy aluminum and the tools themselves are crafted out of high-tensile steel. It is all backed with a lifetime warranty.
3.5 inches long. It should fit into most under-seat bike bags along with your spare tube, a couple of tire levers and a CO2 canister.
More companies need to design stuff like Crank Brothers 19 Function Multi Tool