Description: 【Compact and Portable】: This CW key controller is small , making it portable. It doesn't take up much space during use; wherever you can place a radio and key, there's room for this device 【No Need External Power Source】: The device is no need for an external power source and further reducing dependence on desk space 【Versatile Functionality】: This controller can also be used as a practice tool supporting vertical manual keys, horizontal paddle keys and semi automatic mechanical keys among others. It supports all forms of automatic keys without compromising any functionality 【Easy to Use】: The setup is simple; when used as an exerciser, manual electric keys and automatic electric keys only need to be connected to their respective interfaces; when used as a key controller, the automatic key is connected to its corresponding interface while the radio connects to the output/manual key interface 【Audible and Visual Indicators】: Whether used as an exerciser or controller not only will the buz sound but also blue LED lights will light up in rhythm providing both auditory and visual cues which are especially helpful for beginners in understanding rhythm patterns Specification: Material: PCB   Size Chart: 3.9cmx2.5cm/1.54 inchx0.98 inch Package Includes: 1 Hand Key Oscillator Module 1 Note: Please allow slightly errors 1-2cm differences due to manual measurement.