The Shimano Deore M612 Triple 40/30/22 10-Speed Chainset is a 2-piece design chainset features an external bottom bracket system which is a lightweight rigid design that is incredibly strong & durable. The SG-X chainring with patented spike pins give smooth & fast gear shifts under load. The outer chainring is made from a lightweight aluminium, with the middle steel/glass fibre middle & a steel inner chainrings. The lightweight & rigid steel bottom bracket axle is designed to fit Hollow Tech II bottom brackets. The Deore M612 chainset is great valve & give you many years of service.