The FSA Powerbox Carbon 386EVO uses ANT+ Technology to transmit your torque, cadence, right-left distribution, and performance with accuracy of +/- 2%. Hollow Carbon Arms with UD Finish work together with CNC Machined chain rings for precision and longevity. The chainring bolts are AL7075 Torx T-30 alloy . The 30mm crankshaft is compatible with Shimano Press Fit, BSA, and BB30 inner bearings with additional spacers. The ABS Spider System has sensors on both the left and right sides to measure your power output. Fits Shimano and Sram 10-11 Speed systems, also compatible with Campagnolo 10 Speed. The Bolt Circle Diameter is 110ABS. Available in 170mm, 172.5mm, and 175mm crank arm lengths. Available with Tooth Configurations: 50x34T, 52x36T, and 53x39T.