There are several power meters that will work a Shimano XTR MTB crankset:
Left Crank Arm Power Meter
4iiii PRECISION Power Meter For Shimano XTR M9000 (this will fit XTR 9000)
Stages Shimano XTR M9100/M9120 Power Meter (this will fit XTR 9100)
4iiii PRECISION Shimano XTR M9100 Power Meter (this will fit XTR 9100)
Please also note, whenever you are installing a left side power meter crank arm, you need to confirm you have 10mm of clearance between the left crank arm and the chainstay in order for the sensor to clear. Please see the image below.
Pros: Affordable, easy to install, don’t have to change crankset
Cons: Measures left leg power only
Spider Power Meter
These power meters are compatible with Shimano MTB direct mount cranksets using a 1x chainring such as the M9100. In addition, because they are spider-based power meters, they measure power from both legs.
Pros: Moderately priced, VERY reliable, don’t have to change crankset, measures both legs
Power Meter Pedals
MTB power meter pedals can be installed on any MTB crankset. We have both the Garmin Rally XC and the SRM X-Power.
Pros: Easy to install, works on any bike, can move from bike to bike, don’t have to change crankset
Crankset Power Meter
Of course, you can also choose to replace your crankset entirely for a new one. This is usually a more expensive option, but opens up the door to many possibilities. Here are our Crankset MTB power meters.
Pros: Accurate, reliable, measures both legs
Cons: More expensive, more work to install