The Shimano Deore M615 Double 38/24 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 and durable. The SG-X chainring with patented spike pins give smooth and fast gear shifts under load. The outer chainring is made from a lightweight aluminium, and a steel inner chainring. The lightweight and rigid steel bottom bracket axle is designed to fit HollowTech II bottom brackets. The Deore M615 chainset is great valve and give you many years of service.