Machined housing with four fan-style cooling holes that pump air through the engine while it is running. Rear threaded mounting holes with both 16mm and 19mm hole spacings fits a variety of applications.Specially designed NdFeB magnets with high temperature rating for trouble-free operation. High Temperature 140 Celsius (356 Fahrenheit) rated wire is used for winding the motors to minimize the risk of burning the motor. High quality epoxy coated stator plates on the inner to prevent winding shorts. 0.20mm stator plate id used on this 5010 engine. High quality shielded and permanently lubricated ball bearings are used to control the motor shaft in all of our motors.High temperature adhesives are used to stator windings and prevent them from shifting and pinched or shorted out. 5010 750KV High Torque Brushless Motors for MultiCopter QuadCopter Multi- Aircraft KV (rpm / v): 750KV positive tooth ESC: 20-40A Best works with props from 14-16 inch Engine size: 50 x 10 mm Shaft size: 4mm Material:metal colour:Silver + Black Package Contents: 1 set x Brushless Motor 5010 750KV Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.