The 5Dev R-Spec Bosch E-bike Crank Arms are billet machined from 7075-T651 aerospace aluminum and sized to keep the pedal arc higher off the ground on technical climbs. At the torque loads a Bosch, TQ, or Avinox motor puts through a drivetrain, the material choice is doing real work. What Our Gearhead(R) Experts Are Saying:"The 155mm length is the reason these exist. On a rocky climb where stock cranks clip every other move, these clear the same line without a second thought."