Supposedly the FSA Mega Exo bottom bracket uses the same standard as the Shimano and is supposed to be interchangeable/compatible with the Shimano external design. If buying a new cup/bearing assembly for the FSA cranks is your concern, unlike Shimano, FSA includes (for now) the bottom bracket bearing cups when you purchase a crankset. FSA does not include the tool that is needed to install/remove the bearing cups but the tool that comes with the Shimano DA or Ultegra cranks works just as well (that is what I am using). Personally I think the FSA design is less involved than the Shimano design since FSA uses a crank arm bolt that is similar to the ones used for an ISIS or Octalink bottom bracket on the non-drive side eliminating the need for pinch bolts at the spindle end of the non-drive side crankarm that you find on Shimano's design.

Although I have no experience trying this, several mechanics have made mention that the FSA spindle will fit in a Shimano DA/Ultegra bearing cup set but nobody I asked, other than sliding the spindle into the cups has actually completed such an installation. I have some doubts about this because I think their is a slight difference in the width of the bearing cups of the FSA design as they appear slightly narrower than the Shimano design. The Shimano crank arms fit nearly flush with the external bearing assemblies while my K-Force crank seems to have a slight gap (=/- 2-2.5mm) between the arm and the bearings. Because the FSA assembly seems a little narrower, I think this might cause an FSA crank bind against the bearing surface and eventually overstress the bearings when an FSA crank is used in conjunction with Shimano bearing cups! In short, although I don't know if the parts are interchnageable, I do know that mixing them as described above will more than likely invalidate the warranties for both items!

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I have no time to mess with my bike so I sent mine to LBS to install my Gossamer compacts. Looks fairly simply and so far I love them. I don't understand why there isn't any dustcap for the drive side of the crank. No I gotta clean out another hole after long rides.

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The true Master does not wish to lead,
Nor does he wish to follow.
He only wishes to place himself
Where he is needed most.