It looks like a micro servo, it acts like a micro servo, but it's more than just a micro servo! We got a factory to custom-make these classic 'micro' sized hobby servos with a twist - the feedback (potentiometer wiper) line is brought out to a fourth white wire. You can read this wire with an analog input such as those on an Arduino, to get the servo's position. That information can be used in robotics to improve stability or even allow 'recording' of servo motion.Note that the default servo pulse widths (usually 1ms to 2ms) may not give you a full 180...