All mountain slx hollowtech ii chainset is tough and aggressive yet also lightweight and excellent value the hollowtech ii chainset features hollow forged crank arms which are both lightweight and rigid whilst being incredibly strong and durable hollowtech ii integrated bottom bracket design uses a wide bearing placement with a large axle diameter for increased stiffness efficiency and added durability 10 speed dyna sys chainrings hg x chainring with patented spike pins give smooth a