Shimano XT Mountain Bike Chainset (M770) A high performance chainset from the classic ATB group, using the most advanced 10-speed Dyna-Sys chainrings Forged Hollow Tech II aluminium cranks offer unrivalled strength-to-weight ratio Lightweight construction with external super smooth bottom bracket bearings for efficient use Drilled steel & carbon composite construction middle ring combined with a thicker aluminium double anodized 42 tooth, & plated aluminium 24 tooth ring for excellent rigidity & durability Close ratio gear combination: 42-32-24T provides enhanced cadence while reducing pedal feedback on suspension bikes HG-X chainring with patented spike pins give smooth & fast gear shifts under load Stiffness & strength increased with advanced design due to wider spaced bearings & oversized axle 104 / 64 PCD four-arm chainrings For use with 10-speed HG-X MTB chains only We recommend that this bottom bracket is initially installed by a bike shop to ensure perfect bottom bracket facing & fit Comes complete with bottom bracket for 68 & 73 mm frames Average weight 862 g (175 mm including BB)