Great value 2-piece design 12-speed double chainset All-mountain crank set is tough and aggressive yet also lightweight Forged crank arms 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 We recommend that the bottom bracket is initially installed by a bike shop to ensure perfect facing and fit Direct mount chain ring For use with 12-speed HG MTB chains only With a 51.8 mm chain line for use in conjunction with 142 / 148 mm O.L.D.