The hollowtech ii 10 speed dura ace chainset offers the optimum balance of light weight and rigidity making it the global choice for road racing39s elite ridersshimano has raised the bar to a new level of performance with the development of a hollow outer chainring giving vast improvements in rigidity and increased weight savingsthe hollow outer chainring has essentially removed outer chainring flex hugely improving shift performance making it precise even under high loadthese industry leadin