Shimano XTR CS-M9001 11-Speed 11-40T Mountain Bike Cassette for Triple Cog Sizes: 11 - 40 t Cog Material: [11, 13, 15, 17, 40] steel, [19, 21, 24, 27, 31, 35] titanium Carrier Material: carbon fiber Claimed Weight: 331 g Recommended Use: mountain biking