Features: 36mm diameter, 50mm length, 3.175mm shaft diameter. 4 pole 12 slot high-torque motor design. High purity copper windings maximizes efficiency. Precision engineered for maximum energy conversion. Precision balanced rotor,smoothness for best reliability and maximum RPM. The ESC bulid in 5.8V/3A BEC. Supports program card to make adjustments. Any problem, please contact our store without hesitation. Honor to serve you. Specifications: Item: 3900KV Motor Motor Type: Brushless Motor Watts: 820W Max voltage: