To control the power mode on the shimano steps drive unit use this left hand shifter similar to that for xtxtr di2 this shifter feels exactly the same as the di2 version for a consistent and familiar feel should you get to a part of the trail where riding is not possible you can active walk mode but pressing and holding the shifter down for assist up to 6kph easy to reach without having to move your hand from the grip with adjustable paddles with customisable operation using e tube system