These are inner rotor type brushless DC motors that achieve high efficiency, long life, and low noise levels.
Brushless DC motors are energy-saving DC motors that do not need the commutators and brushes that are the disadvantages of brush motors and provide superior service life, noise levels, quietness, and efficiency. The inner rotor type has the stator positioned outside a cylindrical rotor. It is structurally simple and is the general type motor. Small models have particularly small inertial moments and are easy to change the speed and direction of, so they are also used as actuators in robots and the like.