Replacement crank arms for bafang bbsXX mid drive motors 170mm. Left side crank pedal threads are reverse threaded, left to tighten, right to loosen. Right crank arm pedal threads are standard thread, right to tighten, left to loosen. Make sure to use left pedal in left arm and right pedal in right arm or you risk stripping the threads. Left and right side of the bike are from the seated/riding position.