Hollow Shaft Servo Motor Gun
In hollow shaft servo motors, the gear-shaft extends through the motor shaft and is joined at the motor's crest. 
Therefore,  gear drive unit with a separate structure is no longer required, then resulting in significant weight reduction and compactness.
- Integration of gear drive unit (belt, pulley, servo motor)
- Light weight and more compact size
- Possible to layout plan for Symmetrical design
- Improved maintainability