Originally Posted by
Dan Burkhart
Most MTB external BBs I've dealt with come with 3 spacers. You use from none of them to all three depending on whether you have 73 or 68mm shell, and whether or not there is an E type derailleur.
Bingo. Nailed it. Your crank will have 3 spacers along with the BB. The install should be supremely easy; just make sure your BB shell is faced nicely before proceeding.