I carry a Topeak Alien II with me and used it only once so far. That was to remove a broken link on a BSO and shorten the chain to get the guy back to his car. Three minutes later he had a flat and I had one 27" presta valve tube and he had a 26" shrader valve, but with no tube. So he ended up walking anyway. A couple of months later, I heard that he'd bought a new Cannondale - a T800. So far, I've never broken a chain.