BB-UN26 (-K)- I am replacing the bottom bracket on my Specialized Sirrus and it accepts that type of bottom bracket. The problem is that one of the only models I can find for that have the plastic cups that have reviews saying that it cracks. Are there any compatible bottom brackets that would also work with that? My crankset is a Shimano FC-M391.
Here are some more stats I found about the crankset and bottom bracket combo online: Spindle length: LL 123, chain line- 50mm, shell width=68 / 73 mm (1.37 X 24 T.P.I.)



EDIT: I found a UN 55 bottom bracket with a 68x122.5 length and people in the reviews of the stock bottom bracket said that would work. Possibly?