I was looking at the Shimano UN-54 BB on Amazon, and noticed they didn't have a 68x122.5mm option. There is, however, a 68x122mm option, and I was wondering if that was close enough to or is compatible with a 68x122.5mm BB like the one Specialized says my bike has? Of course, 68x122.5 is available in the cheaper Un-26 BB on there.