Great value Octalink Hollow Tech II chainset for 10-speed Dyna-Sys transmissions Hollow Tech II crank arm is a lightweight & rigid design that is incredibly strong & durable Octalink design HG-X chainring with patented spikepins give smooth & fast gear shifts under load Lightweight aluminium outer with steel/composite middle & steel inner chainrings Dyna-Sys chainset for use with 10-speed HG-X chains