Great value Deore 2-piece design chainset for 10-speed Dyna-Sys MTB HG-X transmissions The 2-piece design chainset features an external bottom bracket system which is a lightweight rigid design that is incredibly strong & durable Lightweight & rigid steel bottom bracket axle SG-X chainring with patented spike pins give smooth & fast gear shifts under load Lightweight aluminium outer with steel/glass fibre composite middle & steel inner chainrings We recommend that the bottom bracket is initially installed by a bike shop to ensure perfect facing & fit 104 / 64 mm bolt circle diameter 10-speed Dyna-Sys compatible