FSA CK-220 Bosch Gen4 E-Bike Crankarms Keep the Power Flowing E-bike drivetrains put more torque through the cranks than a rider's legs ever could alone, and the arms have to keep up. The CK-220 uses diecast aluminum construction to handle that load without adding unnecessary weight to a bike that already tips the scales. The ISIS drive interface connects cleanly to the motor spindle, and a range of arm lengths lets you dial in the fit for the rider on the bike. If you're running a Bosch Gen4 motor and need a replacement armset that just works, this is it. Features Bosch Gen4 compatible designed specifically for Bosch Gen4 motor systems, with compatibility extending to Yamaha PWX and Brose engines Diecast aluminum construction handles the sustained high-torque demands of e-bike drivetrains ISIS drive interface solid, proven spindle engagement for a secure connection at the motor Four arm length options 155mm, 160mm, 165mm, and 170mm to fit a range of riders and frame geometries | Fsa | Ck-220 Bosch Gen4 E-Bike Crankarms 170Mm | Aluminum