The shimano deore m617 chainset 175mm 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 and durable shimano deore m617 chainset 175mm features lightweight and rigid steel bottom bracket axle sg x dyna sys plus chainrings with patented spike pin give smooth and fast gear shifts under load lightweight aluminium outer