The size is comparable to that of an ordinary eraser, and it can be placed in a pencil case, school bag, briefcase, key box or even a pocket. Its size is smaller than that of a key, and it does not take up too much space when in use. As long as there is a place where a key can be placed, it has a place, which also makes it more arbitrary for enthusiasts to choose the place of use. It only needs a CR2032 battery for power supply, no external power supply is required, and it is free from the constraints of the power cord, which further reduces the dependence on desktop space and broadens the use scenarios. (Battery not included) When operating, not only the buzzer will sound, but the green LED light will also light up with the rhythm, and the sound and light will follow the rhythm, making it easy to control the rhythm. For beginners, whether they practice following recordings or practice on their own, the dual cues of hearing and vision help deepen their understanding of rhythm, correct mistakes in technique in time, and prevent QSD (bad hands). For veterans, daily practice not only eliminates the need to rely on larger radios or traditional practice devices, but also allows them to visualize their own rhythm. It supports vertical hand keys, horizontal sweep keys and mechanical semi-automatic keys for left and right operations, and other forms of manual electric keys are also integrated into one device, without compromising with any manual electric keys. No matter what the operation method is, it can be easily mastered with the help of this practice device. Colour:Green Material:PCB The printing/appearance may vary from batch to batch, but will not affect the use Package Contents: 1 x CW Trainer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.