This paper proposes a design of highly reusable hobby servo RTCs (Robotics Technology Component specified by OMG). It is important for ensuring actual reusability of an RTC to define a good design of the RTC which could be commonly used in many kinds of use cases. Command-control is a popular method in hobby servo. Thus we have designed the structure of hobby servo RTCs to resemble the control method. The RTC has two inports and one outport of TimedLongSeq type which emulate a serial line for the control command. In order to evaluate the effectiveness of the design, we implemented the following RTCs and RT systems: we implemented an RTC for a command-type hobby servo based on the proposed design, and built two RT systems, a robot arm and a laser scanner, making use of the RTC. Next, we implemented RTCs for different types of servos, another type of command-control servo and a PWM-control servo, to show the reusability of our design. Finally, we built platforms for humanoid robots using these RTCs to confirm the effectiveness of our design concept in complicated applications.