??High Quality Material?: This bike crank arm is made of premium aluminium alloy, which is lightweight, high strength and deformation resistance, durable for long time use. ??170mm, Diamond Hole?: The center distance between two holes is 170mm without any overlap of crank arm and chain ring bolt; Spindle interface type, diamond hole taper. ??How To Use?: Simple operation, can be completed independently. Note: please check if the orientation of your right crank arm is square or diamond keep both left and right arms having the same hole. ??Efflient Performance?: Standard precision machining, which ensures ultimate chain retention, increases it;s service life, and reduces friction and noise, you won't be annoyed by unpleasant sound, giving you a wonderful using experience. ??Service?: Welcome to order our products and put forward your valuable suggestions so that we can improve and optimize them. If you are not satisfied with the order, please tell us at any time, we guarantee that it will be resolved within 24 hours.