Stages Cycling's Stages Power Meter is a revolutionary power meter that attaches stealthily to the left crankarm. It allows every rider, in every discipline, power-based (also called watt-based) training performance. With advanced technology accurate to +/- 2%, ANT+ and Bluetooth Smart transmitting, active temperature compensation, and mere 20 grams of weight, the Stages Power meter is perfect for any cyclist whether looking for their first power meter or a savvy power-training expert. Additionally, installation is fast, simple, and clean with zero wires, magnets, or zip ties. For mountain bikers, this Stages Power Meter model features Shimano XT replacement crankarms.