The Shimano MT610 12 Speed 51.8mm 36/26T Chainset ?is an excellent value 2-piece design 12-speed double chainset. The HollowTech II integrated bottom bracket design uses a wide bearing placement with a large axle diameter for increased stiffness, efficiency and added durability. Shimano MT610 12 Speed 51.8mm 36/26T Chainset Features 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  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.