The stages power meter shimano ultegra 6800 crank is perfect for riders that want an integrated power measurement device for their ultegra 6800 crank this crank arm replaces your non drive crank arm so you can measure your pedalling power the power meter fits both the compact and standard ultegra crankset the crank uses the new bluetooth smart protocol and ant so you can update the firmware wirelessly you can also upload data from your ride directly from your iphone to your traini