Answering the demand for one by mountain drivetrains, Shimano has engineered the XTR FC M9000 1 one by Race Crank Arms, as part of the new XTR 9000 groupset, to be a light and reliable crank for those who prefer simplicity. The XTR M9000 crank arms are designed with the same hollow armed alloy technology that Shimano uses on its double chainring drivetrains. The slight difference is that that left arm is now hollow bonded to further reduce weight, without compromising durability and stiffness. Without the bottom bracket, the cranks weigh 583 grams. Meanwhile, the right crank arm now sports a four arm spider that, regardless of the one by designation, is compatible with all XTR 9000 series single and double chainring setups. It should be noted that the narrower Q factor, 158mm, while increasing pedaling efficiency, will not work with several full suspension frame designs.