The bmx specific dxr mx71 stages power meter replaces non drive crank arm for existing shimano dxr mx71 model cranks riders looking to add power to their existing crank need only select length the stages power meter fits all current generation dxr cranksetsspecifications accuracy 2 weight only adds 20gr to base crank arm battery life 200 hours coin cell cr2032 power range watts 0 2500 cadence range rpm 20 220 frame compatibility most frames see fit guide in our support