In recent years Shimano has migrated much of their product line away from square taper to a spline attachment called Octalink and to external bearing types. One-piece cranks are easily maintained and reliable, but heavy. The tool for installing and removing these bottom brackets is often also a spline. These external bearings are compatible with those from other manufacturers. Shimano introduced a proprietary splined interface named "Octalink".
Using pressed in standards allows frame manufacturers greater flexibility in frame design that many times offers greater stiffness and weight reductions, however many users are reporting creaking issues with these systems. The term "bracket" refers to the tube fittings that are used to hold frame tubes together in lugged steel frames  which also form the shell that contains the spindle and bearings; the term is now used for all frames, bracketed or not. Their bottom bracket bearing arrangement was a "hybrid" - the right side was internal while the left side was external and had the RS sealed bearing, too. Their special frames have a larger bottom bracket shell allowing the bearings bicycle bottom bracket part be inside again while their top level SI crankarms are still two machined aluminum halves glued together.
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The left side spline interface looks similar, but is different so as to prevent installation of older ISIS Drive crankarms—which are no longer compatible because Q-factor and chainline can not be maintained using these older cranks with an external bearing BB. Some manufacturers make cranks and bottom brackets bicycle bottom bracket part both specifications. Their bottom bracket bearing arrangement was a "hybrid" - the right side was internal while the left side was external and had the RS sealed bearing, too.