This is a NEW Genuine Associated 27441 Reedy Sonic 540-M4 Competition Brushless Motor 7.5 Modified. Part # 27441. However, changes can be good when they serve a purpose. In the case of the 540-M4, the inner bearing has been moved so that it is part of the can instead of the sensor assembly, which more precisely aligns the rotor within the magnetic field while reducing noise and vibration.
eBay