Shimano Deore M5100 2 x 11 Speed Boost Chainset - 26 / 36T. Crank arm length: 170mm or 175mm (choose length). Part Numbers: 170mm: FCM5100BC66; 175mm: FCM5100BE66. Ready for the steep stuff, the fast stuff, as well as the fun stuff, this 11 speed MTB crankset gives you powerful acceleration and smooth shifting performance.