Yuxin timer is an affordable, accurate and stylish timer. It has precision down to thousandths, rubber feet to stand stably on the table, and it fits Yuxin Stackmat and SpeedStacks G4 Mat! Place your hands on the plates until the timer announces that it is ready by turning on a green light. When you lift your hands from the tiles, time starts, and when you put your hands down on it again, time stops. Yuxin hours have sound effects. It has a speaker, and it gives off sound effects when you press the buttons and when you stop the timer. If you think it is superfluous, it is possible to turn it off. The timer can be connected to an external display or a computer, but a cord is not included. Need 2 pcs. AAA batteries. No batteries included.