The LEGO Mindstorms EV3 Education Medium Servo Motor is great for lower-load, higher speed applications and when faster response times and a smaller profile are needed in the robot's design.
The motor uses tacho f eedback for precise control within one degree of accuracy and has a built-in rotation sensor.
More compact than its larger L EV3 actuator brother, the M EV3 actuator fits easily into your tightest robotic mounts, occupying a small volume. Like its predecessor, it uses a tachometric feedback system, providing accuracy to the nearest degree, and has a built-in rotation sensor.
For a slower actuator with more torque, see Actuator L LEGO Mindstorms EV3 Education.