Altegra grade first built-in power sensor • Optimizes all of rigidity, strength, weight and rotational performance • Hollow Glide construction maintains strength while reducing weight for better power transfer and faster precision front shifting. • Most efficient drivetrain • Number Configuration : 50-34T, 52-36T • Crank Arm Length: 160mm, 160mm 5 mm, 17 0mm, 172.5mm, 175mm