When we bought our Burley I had my LBS ask Burley if I could get a different length crank arm for my stoker. The answer was no. We then asked FSA if they would switch out the Burley provided cranks for cranks of the length we preferred. They also said no. I can understand that Burley only orders cranks in 175 & 170, but why FSA wouldn't let us have the length we wanted is harder for me to figure.