4iiii PRECISION Shimano XTR M9100 Power Meter The 4iiii PRECISION Shimano XTR M9100 Power Meter is brings power to your M9100 or M9120 crankset. The 4iiii PRECISION power meter is a left-only crank arm-based power meter and replaces your current left side crank arm. It takes the power that is generated by your left leg and doubles it in order to determine your total power output. Using 3D power meter technology capable of measuring tri-axial strain, the 4iiii XTR M9100 Power Meter is accurate to +/- 1.0%. In addition, it's very lightweight, adding only 9 grams of weight to your crankset. It features 800 hours of battery life and is compatible with both ANT+ and Bluetooth SMART devices. This means it’s compatible with your favorite bike computer, smart phone or tablet. Key Product Details Compatibility: This power meter is compatible with XTR M9100/9120/9130 cranksets. It is also compatible with all other Shimano x100/x120/x130 series MTB cranksets such as the XT M8100/M8120/M8130 or the SLX M7100/7120/7130. Power Measurement: This 4iiii power meter measures left leg power and doubles the value to account for both legs (assumes both legs are generating the same force). The all new 4iiii XTR M9100 PRECISION 3+ power meter features the following improvements over the version 2: Apple Find My which allows you to always know where your bike is! 800 hours of battery life – the longest coin cell battery life in a power meter on the market! Sleeker, slimmer profile making most incompatibility issues a thing of the past. Stronger antenna for even better connectivity. Indicator light for battery life, successful zero-offset and when the unit has been turned on. Advice From Our Staff: 4iiii left side crank arms are some of our best-selling units. They are affordable and easy to install. The one consideration is they only measure left leg power compared to some other power meters that measure power from both legs (those versions usually cost more however). It is more expensive, however it measures power from both legs.