The shimano dura ace r9100 11 speed groupset includes shimano dura ace fc 9100 chainset the hollowtech ii 11 speed dura ace chainset offers the optimum balance of light weight and rigidity making it the global choice for road racings elite riders hollow outer chainring giving vast improvements in rigidity and increased weight savings the hollow outer chainring has essentially removed outer chainring flex hugely improving shift performance making it precise even under high load these