The 105 fc 5800 stages power meter replaces the non drive crank arm for existing 105 model cranks riders looking to add power to their existing crank need only select crank length the stages power meter for 105 fits all styles of 105 crankset including compact and standard standard and black finishes are available specifications accuracy 2 weight only adds 20gr to base crank arm battery life 200 hours coin cell cr2032 power range watts 0 to 2500 cadence range rpm 20 220 w