RT-EM600 E-bike rotors with built in speed sensor magnet providing consistent braking performance through energy controlKey Features:Rotor houses the magnet necessary for speed sensor function on Shimano STEPS equipped E-bikes allowing frame clearance for wider tyres,Compatible with E8000 / E7000 / E6000 / E5000 systems and for rear wheel use only,Rotors are durable lightweight and rigid, using the proven Shimano Centre-Lock system giving increased strength and security with an easy set-up,Precision cut and drilled braking surface improves pad clearing in muddy conditions while aiding cooling under high load,Large alloy spider is a highly rigid and lightweight support for the rotor surface,Super polished braking surface gives excellent braking performance.