All-mountain SLX HollowTech II chainset is tough and aggressive yet also lightweight and excellent valueThe HollowTech II Chainset features hollow forged crank arms which are both lightweight and rigid whilst being incredibly strong and durableHollowTech II integrated bottom bracket design uses a wide bearing placement with a large axle diameter for increased stiffness, efficiency and added durability70 degree spider arm for optimal rigidityFor 11-speed DYNA-SYS11 SM-CRM70 chainring (sold separately)SM-CRM70 chainring teeth feature Shimanos new Dynamic Chain Engagement technology offering enhanced chain retention, driving rigidity and highly efficientWe recommend that the bottom bracket is initially installed by a bike shop to ensure perfect facing and fitFor use with 11-speed HG-X MTB chains onlyWith a 53.4 mm single ring chain line ideally suited for 27.5+ bikes with Boost 148 mm O.L.D.